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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:
Spiritedlight · 25/02/2026 15:06

sellersvin · 25/02/2026 13:09

How did he respond?

It was fine. No major transformations but not bad either.

OP posts:
FunMustard · 25/02/2026 18:13

I have a 14 year old know-it-all son too. It is annoying. Honestly there is nothing you can to make it stop, aside from ride it out. I still tell him what I think, and I tell him off when he's mocking or rude, but ultimately, he's just like I was at that age - couldn't tell me nothin'. I was a brat and a half.

Thehandinthecookiejar · 25/02/2026 18:19

Isn’t this normal teenage behaviour? Thinking they know it all while knowing very little?
I don’t see what harm failing his mocks will do so thing maybe your DHs right.

envbeckyc · 25/02/2026 18:22

My In Laws paid my Husband a cash reward for his GCSEs and A-Levels as an incentive. and needless to say it absolutely worked!

We do the same with our children and it totally works - we put in place individual results payments with bonuses for achievements across multiple subjects.

In total there is a £1000 reward available if all results are in the highest grade. It’s always been very motivating!

ReprogramNeeded · 25/02/2026 18:23

What's his dad like with him?
You can be the most supportive encouraging mum, but it won't help if his dad isn’t doing it as well.

It's unlikely DS really does think he knows it all. He might think he's supposed to, though. Is his dad academically successful, clever, good job?
A lot of boys seem to worry about meeting their father's expectations and about doing as well as/better than them.

Foggyflumpet · 25/02/2026 18:37

Ds was like this in yr10. He also had a slightly unpleasant air of superiority acid him. But I got it- he was lower end of the scale in popularity and cool, so took refuge in being cleverer than everyone else.
Except, he really wasn't.
All his 'I'm fines' came to a head during mocks. He was humbled.

Equally, any attempts to try and outwit us would be met with robust debate. Or:"mate, come back when you've done x, then tell me I'm wrong. "
Or:"show me your evidence."

He's much better now.

Ceceprincess80 · 25/02/2026 18:46

15yr old boys are just know it all pains. I speak from experience of having 22 of them in a workshop today at school. Its a joyless time. Sometimes you have to let them just get on with it but sometimes you need to step in. I would.let him do what he wants for his first round of yr10 mocks, let him do badly then step in with its my way to support you now to pass. They are still kids but think they are adults.

MumInTraining66 · 25/02/2026 18:50

RappelChoan · 24/02/2026 10:21

He’s immature- all adolescents are immature and your role is to support him as he gains life experience and maturity.

He will alternate between wanting the safety of children and the freedom of adulthood, but it’s a teetering sort of time.

You can be a role model for him of a happy and well balanced adult living a good life. Give him something to aspire to but don’t put him under a microscope of what homework has he done. Show him how to disagree gracefully. Be patient and calm. Keep your boundaries.

You sound like this is your area of expertise. Are you experienced in the mindset of adolescents? Ha ha - I may need you on speed dial to help with mine 😉

ChimpanzeeThatMonkeyNews · 25/02/2026 18:53

envbeckyc · 25/02/2026 18:22

My In Laws paid my Husband a cash reward for his GCSEs and A-Levels as an incentive. and needless to say it absolutely worked!

We do the same with our children and it totally works - we put in place individual results payments with bonuses for achievements across multiple subjects.

In total there is a £1000 reward available if all results are in the highest grade. It’s always been very motivating!

My friend (who’s a headteacher) recommends incentivising revision.
And, with some luck, the better grades will present themselves after all the delicious revision!

Flapjak · 25/02/2026 18:58

Foggyflumpet · 25/02/2026 18:37

Ds was like this in yr10. He also had a slightly unpleasant air of superiority acid him. But I got it- he was lower end of the scale in popularity and cool, so took refuge in being cleverer than everyone else.
Except, he really wasn't.
All his 'I'm fines' came to a head during mocks. He was humbled.

Equally, any attempts to try and outwit us would be met with robust debate. Or:"mate, come back when you've done x, then tell me I'm wrong. "
Or:"show me your evidence."

He's much better now.

Mine is very much like this !

janj52301 · 25/02/2026 19:01

I follow a great American comedian. He says teenagers are God's revenge so we know what it's like to make something I your image that then denies your existence

Piknik · 25/02/2026 19:03

I don't think you are aggressive OP and I suspect that underneath it all, your worry is not just him failing but being unlikable. Nobody likes a no-it-all, and when it's your son and you love them, you are forgiving to a point (and you still love them) but when you imagine him talking to peers or even older people: teachers/lecturers/future employers, you sort of cringe for him.

DD had a boyfriend who was like this, talked over us, knew everything, couldn't listen to a story or anecdote without having more/newer/better information or narrative around it. It was tedious and I could see DD cringing. With him, it was being insecure and wanting to impress us. He would have been SO MUCH MORE LIKABLE if he just sometimes shut up, admitted ruefully that he knew nothing about XYZ and listened respectfully.

Teenagers are a bit that way anyway, but your DS sounds particularly annoying and you have a chance to address it now. Rather than focus on what he does or doesn't know - maybe remind him how admirable it is to learn to listen/admit you know less etc, and how it's an endearing quality to be a bit humble in the face of the older and wiser.

Apart from perhaps having that conversation, I would be inclined to go down the 'oh for goodness sake' route. Sort of "don't be ridiculous - of course you don't know more than David Attenborough about the behaviour of Wild Elks, but how did you get on at Swimming today?'

jjW29 · 25/02/2026 19:13

Maybe he just wants to be left alone,as someone else has said it sounds like a coping mechanism,he wants to be in control and not be constantly controlled/interogated by his parents.Ive seen this a lot recently with friends kids and even my own,I don’t really know what the answer is but I would cut him some slack.I know of parents that need to know everything that their child did in school that day and what homework they’ve got etc etc Teenagers don’t need to be micro managed,in a few months he may be working,doing driving lessons,going to parties..you need to let him find his own way.Good luck xx

TheDaysAreGettingLongerAtLast · 25/02/2026 19:16

Maybe he needs extra support at school.
Could you find someone a few years older than him to give him grinds on a subject he is weak on or one he is interested in?
My son does this with schoolboys about 6 years younger and gives them insights into what they need to focus on for college etc.
It may help coming from someone only a few years older he can relate to.

jigglybits · 25/02/2026 19:18

15 year old boys ARE very irritating. A lot of them. I like to think it's nature's way of making it easy for them to leave home.

Piglet89 · 25/02/2026 19:20

I would one hundred per cent let him get on with it his own way and fail his mocks.

Nothing like a good sharp lesson to show him he DOESN’T in fact know it all.

TheDaysAreGettingLongerAtLast · 25/02/2026 19:23

Piglet89 · 25/02/2026 19:20

I would one hundred per cent let him get on with it his own way and fail his mocks.

Nothing like a good sharp lesson to show him he DOESN’T in fact know it all.

I wouldn't - it could crush his confidence.
His bravado is just that.

ChimpanzeeThatMonkeyNews · 25/02/2026 19:24

Piglet89 · 25/02/2026 19:20

I would one hundred per cent let him get on with it his own way and fail his mocks.

Nothing like a good sharp lesson to show him he DOESN’T in fact know it all.

That’s a bad idea.

DotAndCarryOne2 · 25/02/2026 19:25

NoFiller · 24/02/2026 10:09

Your husband is very knowledgeable about astrology?

Not surprised your son is telling him he’s speaking bollocks.

I took it to mean astronomy.

Contrarymary30 · 25/02/2026 19:25

Spiritedlight · 24/02/2026 10:14

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

I assume you mean astonomy ?

DotAndCarryOne2 · 25/02/2026 19:26

Contrarymary30 · 25/02/2026 19:25

I assume you mean astonomy ?

Yeah, it’s not rocket science !!

DotAndCarryOne2 · 25/02/2026 19:27

TheDaysAreGettingLongerAtLast · 25/02/2026 19:23

I wouldn't - it could crush his confidence.
His bravado is just that.

Agree. The short sharp lesson shouldn’t be one that could affect his future.

ChimpanzeeThatMonkeyNews · 25/02/2026 19:29

Metaphorically, you only want him to graze his knee, somewhat, not fall off the wall entirely, and smack his head against the concrete.

Piglet89 · 25/02/2026 19:31

TheDaysAreGettingLongerAtLast · 25/02/2026 19:23

I wouldn't - it could crush his confidence.
His bravado is just that.

Totally depends on his personality whether it’d crush his confidence.

@Spiritedlightwould the short sharp shock of failing mocks help or hinder?

Kids these days are way too mollycoddled by parents for too long. If he thinks he knows better, just let him get on with it, I say. I honestly cannot be hooped with this kind of crap.

gingerninja · 25/02/2026 19:31

It’s not just a boy thing, this is just what teenagers are like. Thankfully mine are mostly out the other side and are happy to take advice again. I found the exam years horrible. I get that you’re worried but I suspect he is too and perhaps he’s finding your worry too much pressure. My advice would be if he’s saying he’s doing enough then take him at his word. He will be being reminded on a hourly basis at school how important exams are, the pressure from school is immense. Providing an environment where he doesn’t feel judged is far more important at this point. He needs to feel relaxed and safe at home and somewhere he can escape to not from. I say this with kindness, I learned the hard way that adding pressure can be really damaging for a relationship and their mental health. That doesn’t mean you don’t have any rules but they have to take accountability for themselves and sometimes they do have to fail. I always say to mine, ‘your decisions, your consequences’ and I mean it.