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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

15 year-old know it all son

308 replies

Spiritedlight · 24/02/2026 10:00

Hi everyone

I would like to have thoughts on how to handle/progress with son. He's 15, smart, lovely, very opinionated, completely resistant to being told anything and thinks he knows it all.

For example, a discussion about astrology/space etc - whilst DH is very knowledgable, DS will disagree with everything DH says, and quote, frankly, bollocks a lot of the time.

If we talk to him about the school's recommendations for self-study in Year 10 - which I know he's not doing, because I know what they expect - e.g., 2 x 30 mins of going over triple science lessons a week -he will completely tractor over the discussion with comments like, "I'm doing it through homework, it's about quality not quantity (he does the bare minimum), my grades are very good (not as good as he thinks) etc etc". Everything gets brushed off, diminished, he knows best. Always.

It's the oddest, most annoying thing. I've tried to talk to him about it but I don't get anywhere - except that he thinks we are telling him off, which suggests to me this is a defence mechanism. And we are really not telling him off in those moments, we're trying to open up conversation and be supportive about these school years.

I'm worried about his grades and how he's just going to not fulfil his potential. DH thinks let him get on with it and fail mocks etc, so he'll see for himself. But I don't know what to do.

OP posts:
Noononoo · 25/02/2026 21:38

Yes I remember getting through to my son who was dropping out and never listening by telling him that exams were like an intelligent game.. the passes were like tokens he could exchange to get to the next level if he chose.. he’s not doing it for you it’s for himself for more choices in the future. Nd he seemed to get that and it stopped him thinking it was a power game between us and him in which he felt he had to rebel. I know it sounds mad but it is a kind of truth.

neilyoungismyhero · 25/02/2026 21:45

Sounds like my grandson.

Laurmolonlabe · 25/02/2026 22:27

TBH he really doesn't sound lovely- being smart and very opinionated are almost mutually exclusive.
I'm not sure what you can say to him that will get through to him.
the only cure for this kind of arrogance is life itself- I'd put my hands up and say "well you know best then, we will see what happens".
Truly you cannot prevent another human being from making a mistake all you can do is try to bring them to a place where they can see it for themselves- I'd hold on tight , don't be critical and hope you can ride it out.

lightand · 25/02/2026 22:35

I dont expect this has been mentioned before on here.

This is what I did.

At a calm time, I told the young person, we are going to play out a scenario.
All very calm.

I told them to go out the door and I will write things on pieces of paper.
Told them to come in when I was ready.

When the person came in, I handed them a piece of paper.
Told them it was August.
And this was the grades I was expecting them to get, the way the person was going.
I did it all very realistically.
I asked the person what they thought.
They were not best pleased.

Then I told them to go out again.
Repeated the episode.
This time I had ready the grades I thought they could achieve if they were sensible going forward.
Asked them what they thought.

It all worked.

Thechaseison71 · 25/02/2026 22:37

Octavia64 · 24/02/2026 10:19

Firstly, many teenage boys are like this.

arguing with them just feeds it.
focus solely on outcomes. Is he doing as well as he wants to at school? If not then put rewards and consequences in place. If so then ignore as much as possible.

on a separate note I think you have confused astronomy and astrology. Astronomy is the scientific study of stars.
astrology is the belief that the stars impact how we act on earth through our star signs (which stars were in the sky when we were born) and I don’t think anyone really believes in it these days

I have 3 brothers and they ALL knew better than everyone else as teens

SemiRetiredLoveGoddeess · 25/02/2026 22:40

Last two posts with advice you have. said were rude. Do you mean rude like your son?

ChaliceinWonderland · 25/02/2026 22:46

It's normal! Just don't engage when he's like this. Smother him with praise. Use behaviour strategy techniques.
Walk away if he tries to initiate. I havec15 year old and c16 year old I'm a single mum. They do try it on... but rarely. I just wouldn't tolerate that in my house.

Dumpspirospero · 25/02/2026 23:47

2026ontheway · 24/02/2026 13:13

Did you find the sport helped him (or you!) get through this stage? We’re just about to get into this stage!

I do think team sports or sport in general can be really helpful here. Once they are in a team, they have to suppress their egos a little bit to work together and get the win. Then there is the discipline and the need to take instruction. Coaches won’t mince their words if they are out of line. The praise they get when they play well will be the best. They become truly knowledgeable about something (their sport) so don’t have to blag and can hone their critical faculties watching/ commenting on the professional game. Developing relationships with other adults, such as coaches or one-to-one tutors (if they have these at his school) can be really beneficial too at this age when they are separating from parents and need to be seen as individuals to be respected in their own right.
It does sound like a defence mechanism and one he’ll grow out of. I’d definitely keep it factual and challenge the bullshit but be kind and gentle too.
Teenage boys can be great fun and v funny. One of y DCs had slight know it all tendencies at that age. She was challenged on the facts when she spouted nonsense and deferred to when she really did know more about a subject. She went down the path of reading tonnes, listening to podcasts casts, watching documentaries and studying hard. She’s now genuinely knowledgeable on lots of subjects and much less likely to assert her opinion.
Keep the discussions round the table going. Even if it drives you nuts, this is how they learn to debate and deal with the opinions of others.

TheCheekyCyanHelper · 25/02/2026 23:55

Spiritedlight · 24/02/2026 10:00

Hi everyone

I would like to have thoughts on how to handle/progress with son. He's 15, smart, lovely, very opinionated, completely resistant to being told anything and thinks he knows it all.

For example, a discussion about astrology/space etc - whilst DH is very knowledgable, DS will disagree with everything DH says, and quote, frankly, bollocks a lot of the time.

If we talk to him about the school's recommendations for self-study in Year 10 - which I know he's not doing, because I know what they expect - e.g., 2 x 30 mins of going over triple science lessons a week -he will completely tractor over the discussion with comments like, "I'm doing it through homework, it's about quality not quantity (he does the bare minimum), my grades are very good (not as good as he thinks) etc etc". Everything gets brushed off, diminished, he knows best. Always.

It's the oddest, most annoying thing. I've tried to talk to him about it but I don't get anywhere - except that he thinks we are telling him off, which suggests to me this is a defence mechanism. And we are really not telling him off in those moments, we're trying to open up conversation and be supportive about these school years.

I'm worried about his grades and how he's just going to not fulfil his potential. DH thinks let him get on with it and fail mocks etc, so he'll see for himself. But I don't know what to do.

This is completely normal for teenagers. They grow out if it, or become politicians.

ForQuirkyFawn · 26/02/2026 01:23

Typical 15 year old then....

Chickadee001 · 26/02/2026 02:47

Spiritedlight · 24/02/2026 10:00

Hi everyone

I would like to have thoughts on how to handle/progress with son. He's 15, smart, lovely, very opinionated, completely resistant to being told anything and thinks he knows it all.

For example, a discussion about astrology/space etc - whilst DH is very knowledgable, DS will disagree with everything DH says, and quote, frankly, bollocks a lot of the time.

If we talk to him about the school's recommendations for self-study in Year 10 - which I know he's not doing, because I know what they expect - e.g., 2 x 30 mins of going over triple science lessons a week -he will completely tractor over the discussion with comments like, "I'm doing it through homework, it's about quality not quantity (he does the bare minimum), my grades are very good (not as good as he thinks) etc etc". Everything gets brushed off, diminished, he knows best. Always.

It's the oddest, most annoying thing. I've tried to talk to him about it but I don't get anywhere - except that he thinks we are telling him off, which suggests to me this is a defence mechanism. And we are really not telling him off in those moments, we're trying to open up conversation and be supportive about these school years.

I'm worried about his grades and how he's just going to not fulfil his potential. DH thinks let him get on with it and fail mocks etc, so he'll see for himself. But I don't know what to do.

I'm guessing you mean ASTRONOMY?!

persephonia · 26/02/2026 02:53

Spiritedlight · 24/02/2026 10:14

What kind of comment is this? That's just rude

Do you mean astronomy or astrology?

persephonia · 26/02/2026 02:59

persephonia · 26/02/2026 02:53

Do you mean astronomy or astrology?

Sorry I just saw you already responded to someone else re the astrology thing.

As others said it's a phase. A very annoying phase. I was a know it all at 15/16. And TBF I do think I was right about some things but it still must have been super annoying for my mother. Possibly he will discover politics next which will be really fun for all of you. But I think it's part of learning more about the world, especially moving beyond the scope of your parents and getting more independance and independent thought. Which is all lovely. It tends to result in some annoying know it all behaviour short term.

Poodlemother4 · 26/02/2026 07:34

This is quite natural in teenagers. They think they know everything and only experience will teach them that they don't. That is why young people join the army to fight, thinking that they are invincible and nothing bad will ever happen to them. I agree, it is tedious, also pointless to argue. I would suggest that future conversations could be conducted like this: You ask a question about how he would cope with a certain situation eg the unlikely event of your house being struck by an earthquake. What would be the first thing he would do? Where would you all live? What about water and food? Heating lighting and clothing, bearing in mind that all has been consumed by fire. Don't argue with him, just listen to what he has to say eg "I see, and supposing you couldn't immediately find food, what would you do?" If the answer is go to a friend's house, you can say "Ah, but their house has fallen down as well. And so on and so on. Do it in small sessions, so you don't make his brain implode, it will teach him that he doesn't have all the answers and that maybe parents might have some which fit. Hope this helps.

LaDamaDeElche · 26/02/2026 07:45

Although annoying it’s pretty standard teen behaviour. My 16 year old DD is very similar. I try not to get into it with her. She’s very into chat gpt, so when she’s talking rubbish with full conviction I tell her to ask chat and that usually ends the know it all conversation 😂

Regarding school it’s a tough one as obviously you want him to do well. You can’t force someone to study though. Is there any kind of intermediary, like a teacher he respects or older teen, who could have a conversation with him? I think with strong-willed teens like this often punishments don’t work, but perhaps something to motivate him instead? Something he wants that you’ll get for him if he gets x grades in his mocks, maybe.

Popsielady · 26/02/2026 09:57

Yes we’re getting exactly the same with our son, in his final year of a-levels any advice gratefully received!

creeeepy · 26/02/2026 12:08

15 year olds - boys and girls - can be the MOST irritating, rude and, obnoxious beings. I know I was too.
Thank goodness 99% of them grow out of it into lovely humans.
You’ll laugh about this in years to come.
Stay strong and stick to your principles.

Evidemment · 26/02/2026 12:11

For what it's worth OP there's evidence in this thread that some folks do retain the trait of self importance and continue assuming they know better even into adulthood. Goes to show you're not alone in suffering this!

(See the endless posts about astronomy/astrology and repetitive Mark Twain quote - the thread/relevant info clearly isn't read before jumping to give their enlightened input 😉)

JustMeAndTheFish · 26/02/2026 12:38

HelenaWaiting · 24/02/2026 10:11

We dealt with something similar by dealing solely in facts - what does he want to do next, what grades in what subjects does he need, where is his progress towards those grades. That's all GCSE results are, at the end of the day, just a passport to the next phase. 8s and 9s are nice, but within a very few years, no one will care or even ask what GCSE grades he got. Take the emotion out of it, stick to the facts. Worked for us.

With all due respect this isn’t always true and depends on the career/job he actually wants.
In general I agree that every step on the education ladder is just that - a way of progressing to the next step.
My daughter works in STEM, has two post grad degrees and has recently been asked about her GCSE and A level choices and results.
The post she was applying for had over 150 applicants so I presume they were all equally qualified and they had to differentiate somehow.

Soberinthecity · 26/02/2026 13:22

BlueMoonBlueCheese · 24/02/2026 10:15

Maybe it was intended to make you reflect.

Why does he think you are telling him off?

Children's communication skills are a reflection of their parents communication skills or lack thereof.
Maybe you don't realise it but the tone you are using is critical, negative etc.
Maybe you never praise him, it's hard for any reader to say with the limited information.
Maybe try and take him for a meal or a walk and talk about the good things in his life and gently try and find out if there is anything worrying him?

definitely all of this. A walk or drive and talk is far better as there is no eye contact and therefore nowhere near as confrontational. Maybe he doesn't like school at all...I was the same at 15; couldn't wait to get out of school and I always knew best. Bright but F*cking lazy and complacent. I'm 54 and a psychotherapist and ex-teacher (go figure...) so it didn't do me any harm.

point is - there may be other things going on; as if being 15 isn't hard enough! It's too old to be childish, too young to be an adult....they're all over the place. Are there other siblings? there's so little info provided it's hard to know what advice to give but patience, clear & consistent boundaries and a ton of love will be a good start. There are way more important things in life than good grades.

Lunaticmess · 26/02/2026 16:26

JustMeAndTheFish · 26/02/2026 12:38

With all due respect this isn’t always true and depends on the career/job he actually wants.
In general I agree that every step on the education ladder is just that - a way of progressing to the next step.
My daughter works in STEM, has two post grad degrees and has recently been asked about her GCSE and A level choices and results.
The post she was applying for had over 150 applicants so I presume they were all equally qualified and they had to differentiate somehow.

True. A lot of employers ask about A-level results these days because they are still considered harder than degrees for a lot of professions.

focused1 · 26/02/2026 16:57

As a mum of 5 boys which are 10 years apart I know most 15 year olds put on the 'I am not worried ' front . Check with subject teachers at school how he doing then have more of a practical talk of what he plans to do post school . Both attend a careers advice session and see they will explain grades he needs for apprenticeships , college , uni to give him some goals .
Distraction next year might be a part time job so he understands having his own money and an excuse to part him from some of his friends who might be thinking the same things but deep down they are also worried and think there is no other pathways apart from intense study .
After exams I would ask for school support . Group study as asking any 15 year old to study on their own even for 30 mins is totally stupid ,
Wouldn't threaten anything but get others outside the family to provide help.He isn't laughing inside - this is usually a front at this age.

Foggyflumpet · 26/02/2026 20:21

Been thinking about this a bit more. I wonder if it's because you FEEL everything so much more as a teen. I do have (suppressed!) Memories of KNOWING I was right and NEEDING other people to recognise it.

I no longer care😄 There really do become bigger things to think about. And you realise that it's no way to keep friends😄

cantbebothered101 · 27/02/2026 08:44

Op here’s a good link on brain development it might help a bit!

www.instagram.com/p/DVBxAZykiIh/?igsh=bWYwbmhzZ3ZvYWM%3D&wa_status_inline=true

smurfingbutgenerallynice · 27/02/2026 11:39

Spiritedlight · 25/02/2026 19:53

I don't know. But it feels weird letting him fail to teach him a lesson. It goes against my maternal instinct.

It is not a good idea to let him fail.
Work out what he needs to do by looking at his books, and tell him what he needs to do, and tell him that whatever he says you are there to support him.

And give him resources which correct his wrong ideas in relation to astronomy and everything else. The DK encycs are amazing even for this age (younger kids read them) because of content but also because they open up discussions. Your dc could be talking to your dh at the same level in relaton to astronomy and that is more what you want. The DK Space encyc for example would tell your dc a lot of information and give him confidence to discuss and to explore the area himself. As for politics or other subjects, there is no right or wrong, give him your informed opinion and say "but this is just my opinion, I am not necessarily right" and only correct factual errors. It will end up with your dc asking your opinion on stuff, knowing that you won't force him to agree

So for exams: give structured help and rewards
Other stuff: give resources and give your opinions but keep it at debate level rather than telling him

The posts telling you to let your dc fail are bonkers. If your dc is not doing as well as they should whether they tell you the opposite or not. No 15 year old, ever, said "oh dear I panned in my mocks, I had better work hard now".