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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:
Calliopespa · 24/02/2026 15:28

LidlAmaretto · 24/02/2026 15:04

It did make me laugh to think of a grown man having an argument with his DS about whether being a Gemini really makes you indecisive!

Laugh away: the op came for constructive help.

Dontgetitt · 24/02/2026 15:30

All those saying ASD or whatever ... it's a completely normal piece of teenage behaviour.

Dd has always been like this and still is at 22. If you produce stats to prove one of her arguments wrong she says they're rigged. I tell her she's like Donald Trump. The penny usually drops although she won't admit it. He'll be fine, OP, relax

Deadringer · 24/02/2026 15:30

Most 15 year old boys are annoying know it alls, many of them don't grow out of it.

RobinEllacotStrike · 24/02/2026 15:35

NamingNoNames · 24/02/2026 14:13

What a pointless thing to say.

someone already said that on page eleventy-four

smurfingbutgenerallynice · 24/02/2026 15:38

Muffinmam · 24/02/2026 13:22

He doesn’t sound smart - he sounds narcissistic.

An intelligent person doesn’t argue about things they know nothing about.

My brother was/is incredibly intelligent. He was gifted as a child and coasted through school without any effort.

He argued about things he knew about and as an adult he is extremely well read and now works in a STEM field.

The problem with gifted children is they can burn out after highschool. They grow up knowing they were the smartest in their entire school and never had to try. At University they are often not the smartest and need to actually show up to lectures or they will fail.

There’s also the possibility that a person can be so intelligent they can feel ostracised from their peers and suffer terrible mental health.

I don’t think your son is at any risk of either of the above scenarios.

I suggest you encourage your son to pursue a trade if his grades are bad. Also, if he’s arguing about things he has no knowledge of he will completely fail at University as no one will put up with his BS.

As a parent it is your responsibility to prepare your children for society’s expectations and part of that is social intercourse. Without social skills he will fail to establish a social network at University or in any workplace which will very much limit his career options.

I don't agree with some of what you have said here. How well people do will depend on the sort of stimulation they had as a young child, the resources made available to them, the support and encouragement they get. It isn't helpful to label teens as gifted or narcissistic, I don't think. Better to work out what support they as individuals need to move forward. Coasting doing well without trying indicates potential, but it also indicates emotional problems holding someone back from really putting their heart and sould into something and finding their passions.

An able teen might argue about things they know nothing about if they feel anxious, scared, at that moment.

I do agree about the potential for bullying and burnout but what you say about social intercourse is relevant in relation to dealing with this too - burnout and being badly affected by bullying is less likely where there are high levels of emotional intelligence, and emotional intelligence is also a taught skill, part and parcel of teaching about social intercourse...

What STEM field did your brother go into?

NettleTea · 24/02/2026 15:38

I know that my kids have said that I can sound like Im giving them a lecture and going over the same thing several times in several different ways why Im trying to make a point. Ive learned to just be succinct and say it one time only.

But if he is a know it all regarding school work, then I agree to let him see he isnt so great and mess up the mocks. TBF thats kind of what they are there for.

Libra24 · 24/02/2026 15:40

15 is prime age for the emotional part of the brain developing faster than the Reasoning centre. It's also the time of testosterone surge and establishing independence.
It sounds unbearable and you sound sad that you've failed in some way. But you 100% haven't.

Could you all sit down together and just establish the basics of respect again, when he's not feeling quite so testing. Eg, you can ask a question or present an alternative opinion but you can't tell me that I'm wrong. No name calling/ using slang or rage baiting. Don't use words like stupid or annoying when describing each others actions or beliefs. Etc etc etc.
And just clarify that whether or not he intends to be upsetting, you are feeling upset at how he is behaving.
Perhaps a safe word for when you all just need to step away before tempers fray too far. You say you are good at repair which is positive, it would save your feelings a bit more if the situation never got that far. You've acknowledged you can be perceived as critical, so again, a way to stop the discussion in its tracks might help you both. Its not punishing either party, it's trying to keep things on a respectful basis.
Honestly I'm realising this is how I parent my toddlers hahaha so hopefully I'm ready for the next season of life

Boomer55 · 24/02/2026 15:43

All teenagers think they know it all. They don’t, but it’s something that’s always happened. I thought I knew it all. 😂😂😂

A few years of working and being an adult soon sorts it out. Meanwhile, just agree and smile. 👍

ChimpanzeeThatMonkeyNews · 24/02/2026 15:46

I thought it was pretty obvious that the OP meant astronomy.

ChimpanzeeThatMonkeyNews · 24/02/2026 15:46

I thought it was pretty obvious that the OP meant astronomy.

ChimpanzeeThatMonkeyNews · 24/02/2026 15:46

I thought it was pretty obvious that the OP meant astronomy.

ChimpanzeeThatMonkeyNews · 24/02/2026 15:46

I thought it was pretty obvious that the OP meant astronomy.

ChimpanzeeThatMonkeyNews · 24/02/2026 15:46

I thought it was pretty obvious that the OP meant astronomy.

ChimpanzeeThatMonkeyNews · 24/02/2026 15:46

I thought it was pretty obvious that the OP meant astronomy.

UnctuousUnicorns · 24/02/2026 15:51

We heard you the first time! 🤣

GasPanic · 24/02/2026 15:52

smurfingbutgenerallynice · 24/02/2026 15:23

I have experience of this. I think teens talk like this when they are very stressed, they know they have left things to the last minute, they are anxious about the future, they know they haven 't done enough work, things like that. But they won't say that and in fact may not even have processed the thoughts fully enough to be able to give them words.

I suspect that your dc knows that they are clever but they also feel anxiety, perhaps about being behind.

In relation to the astronomy discussion, your dc is arguing and perhaps making things up because he wants to know about it and wants to have an intelligent discussion about it. So buy him a dk encycopeadia of space, it is brilliant and full of engaging fascinating info. And buy him other dk's while at it.

Your dc probably feels threatened by your dh for good reason on some level so worth thinking that through

Teens who coast (do well enough without trying at all - but not as well as they could) won't find their passions unless they really put their heart and soul into their learning. Coasting is not doing them any favours. I think it is worth talking about this and saying that you can support your dc's learning and that you can help him do well and say it a lot until it gets through

I wouldn't let your dc fail his mock to show him, it will affect his confidence and stress levels and make it even harder to revise.

While waitiing for him to listen, you could have a look at his work and make a plan for each subject about what you think needs doing to get him up to speed, and think of nice bribes to motivate each stage and then just force it through with him, getting him to learn bits with rewards at a time until his natural self motivation comes alive. I realise they are 15 but this is a hard time to be 15 and there will be a lot of influences in their lives taking them in the wrong direction.

It isn't a boy/girl thing incidentally. Girls are like this too if they know they could do well and secretly want to do better but feel a bit behind and stressed out.

Edited

A dk encyclopedia of space ? lol. I would have chewed that up and spat it out at 15 years old. Probably at 10 years old.

He needs to go on the web. And it's cheaper.

Nasa site, Drbecky is a good youtube channel which is a bridge between "popular level" astronomy and more serious professional stuff, as is the Space site.

If you want to show him how much he doesn't know about astrophysics, a trip over to arXiv and download some of the astrophysics papers on there and have a quick read of some.

QuaintOrca · 24/02/2026 16:07

Teenagers are like this for a reason, psychologically there's huge changes happening in the brain where anything a parent says will be instantly wrong. It's part of teens developing independence skills and an ability to take responsibility. At the end of the day, if he gets shit grades it will teach him a lesson. Just because we know they are saying incorrect things doesn't mean we should always challenge them, being a teen/yo is all about figuring it out by yourself. As a parent, ask questions not criticisms. Teach him how to make his arguements stronger not louder.

We are a generation that's coddling teens way too much and it hinders their ability to become self assured adults. We learn best when we fail and we will be there to wipe tears and listen deeply but at 15, unsolicited advise will always be taken as a criticism.

Alittlefrustrated · 24/02/2026 16:18

RosesAndHellebores · 24/02/2026 10:24

@Spiritedlight this too shall pass. At 15 DS would argue the wall was black, not white. We tried hard to deflect the comments but it was a challenging time with little or no listening to other perspectives. He had uncontestable views based on many things: politics, the police, social justice, liberal arts v stem, his headmaster, whether the sun was fucking shining.

He's 31 now, married, expecting a baby and has a PhD. He started to revert to his chilled, sunny self when he was about 22, getting back to base at about 25 when I think the frontal cortex is fully formed. Be glad he has the confidence in his nurture and security at home to kick off at home. At this stage it's all about the export model.

Bloody hell, I'vw got another 10 years if this?? 😭

UnctuousUnicorns · 24/02/2026 16:26

Alittlefrustrated · 24/02/2026 16:18

Bloody hell, I'vw got another 10 years if this?? 😭

Move to Scotland and pack them off to Uni at 17, preferably on a 5 year course, maybe PhD or other post grad after? It'll pass a few years away.

Slightly light-hearted, obviously.

RosesAndHellebores · 24/02/2026 16:27

@Alittlefrustrated and the previous poster who said this, it improves afyer 2/3 years, then they go to uni, and by 21 they are less argumentative and it gets better bit by bit. A hard Paddington stare at DS coupled with the words "do you actually want some help with your expenses for your Masters/PhD" worked wonders.

DD has never been argumentative but was challenging in different ways, like the eating, the anxiety, the cutting - give an argument any day. She's still at home, nearly 28, doing really well, great job.

murphys · 24/02/2026 16:57

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 really think sport helped him in so many ways.
Socially - (he had always been socially akward) so being in a team was important
Physically - there is nothing better than a teen getting out there getting fit and in turn, letting off steam at the same time.

I can think of no negatives (ok maybe getting up at silly o'clock to travel for matches, cost of kit etc, but this is a given).

But for us I think the top benefit was having older male figures to look up to. I'm a single parent and he was the only male in the house. One of the sports is martial arts and he thrived so under the guidance of adult males that he could look up to. They really took him under their wing and he really flourished. They were also not afraid to put him in his place when necessary. MA is a very disciplined sport anyway, so being out of line wasn't taken lightly.

He did push his luck during those 14-16 aged years, like every boy in that age group that does. But he had a very good outlet for when he needed it too.

Honestly imo if any sport is an option for your ds, I really think it's so beneficial for them. My ds even travelled overseas with his, so that again was another really fantastic benefit.

Sausages123456 · 24/02/2026 17:00

Havent read it all, but yeah I've got one of these at home. TBH I've backed right off, if he doesn't try hard enough now he's got a lot of work to make up next year in Year 11. My DS does bare minimum studying, did ok in his last set of exams but looks at me like I'm talking crap when I say you need to study more.
I remember being that age. They'll realise!

Galatine · 24/02/2026 17:08

This thread reminds me of the Mark Twain quote:
When I was a boy of 14, my father was so ignorant I could hardly stand to have the old man around. But when I got to be 21, I was astonished at how much the old man had learned in seven years.”

Firebox64 · 24/02/2026 17:13

Arguing with a teenager is like mud wrestling with a hog. You both get covered and the hog loves it.

smurfingbutgenerallynice · 24/02/2026 17:15

GasPanic · 24/02/2026 15:52

A dk encyclopedia of space ? lol. I would have chewed that up and spat it out at 15 years old. Probably at 10 years old.

He needs to go on the web. And it's cheaper.

Nasa site, Drbecky is a good youtube channel which is a bridge between "popular level" astronomy and more serious professional stuff, as is the Space site.

If you want to show him how much he doesn't know about astrophysics, a trip over to arXiv and download some of the astrophysics papers on there and have a quick read of some.

Chew up and spit out as in it is not advanced enough for you? But you aren't the one arguing without facts? It is definitely the right level for someone who doesn't yet know much about the subject and it is well written and interesting, it would give confidence to someone who wants to debate something as it gives a broad base of information.
It is written by those with expertise, even if not for people with expertise
Web is fine if you already have some baseline knowledge and you have a specific point to look up. And the nasa thing would be good for someone who already has an interest there.

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