I don't know if I'm being silly even asking this but...
DS is in year 8. My impression has always been that he's very good at maths. At primary school he was very quick and even now he's super fast at mental maths type things - always the first in our family to come up with an answer to "every day" number things. At the end of year 6 his CATs score for the "quantative" test was 137 which I think is high but his non verbal was much lower at 108.
However he seems (to me, and I have no specialist knowledge) not to be doing as well as I would have expected. He's always seemed to be someone who just "gets" numbers but he's struggling a bit with things I would have considered relatively straightforward eg multiplying out brackets; eg in (y+4)(z- 3) he'll often get -1 for the last number instead of -12 because he forgets it's a multiplication. He can do it fine when he remembers but he doesn't seem to have that understanding of what he needs to do that he's always had. Similarly they've just been doing sums such as "increase by 24%" and instead of multiplying by 1.24 he's still trying to do it by working out 20% of the number, then 20% of that number then adding both of those to the original number - all correct but slow! And not possible when the numbers are complex.
I understand his teacher has a reputation of being the weakest maths teacher in the department but (although he doesn't really like the teacher) ds doesn't feel the teaching is not good; he does know what he's meant to do but he has to remember what to do rather than it coming naturally. He misses about 40 minutes of maths every 3 weeks due to a music lesson (they do 3 hours of maths a week) - I wouldn't have thought that would make a massive difference? (If it would we can deal with this).
He's solidly in the upper half of the second set. He has always been better at maths than his sister (who's harder working but easily thriving in top set - though obviously in a different cohort. But thinking about it she does very well in those maths challenge that schools do and he does less well generally).
We have parents' evening next week and I'm not sure what to bring up, if anything. I'm sure he's doing "fine"; it's just that he's always found maths straightforward and I don't know if this change is common? (Only have dd to compare with and I would say she's enjoying maths more now that she's doing trigonometry etc and I can only envisage ds hating it).
Sorry for the essay and hope it makes sense!

I think you may have hit on the difference between mental arithmetic and mathematical concepts.

Primary school seems to me to be more about the former and secondary school more about the latter.

My DD had the opposite in that her mental maths wasn’t great (if she practised she got better, but she didn’t want to) and as a result started year 2 in the bottom maths set at primary. However she had also worked out, by herself, what her 20 times table was from her 2 and 10 times tables, purely because she had completely understood the concept.

It sounds like he might need some better explanation of the concepts so he grasp them.

The examples you quote are interesting - moving from fnding a % and adding it on to getting the answer by multiplication is a big step in understanding. His approach is fine but slow and when he comes to an awkward number will take FAR too long.

Ditto expanding brackets.

What would I do? Brackets - go back to basics - can he expand 3(2x - 5) consistently? If so then can he do x(2x - 5) + 3(2x - 5) and get it right? If so then I'd suggest that he breaks down (2x + 3)( x - 2) to 2x( x - 2) + 3(x - 2) untl he remembers he is multiplying.

To move to the multiplicative way of working out % - has he been taught this yet? Understanding increase and decrease like this might not be taught in Year 8. If it has then get back to me.

Tinkers and G55, thank you so much for getting back to me. It sounds as though maybe I was inadvertently expecting too much!
Tinkers maybe my dd was more like yours which is why she's find it easier as she's got older. I do think he needs the concepts explaining better - I think I can do that at the moment but I might struggle as he moves on (I have maths A level but can't remember half of what dd is doing in GCSE ).
G55, thank you. I hadn't realised that was such a jump forwards. They have been taught the multiplying for increase and decrease and now I've explained it to him he did get it. I think I was just surprised (and it sounds as though that was unfair!) that it wasn't "obvious" for want of a better word. It's really useful to know that concepts like this can be tricky. He missed a large part of the lesson where it was explained though.
Thank you.

As someone with a Maths degree now working in Learning Support it has become painfully apparent to me that many things which seem "obvious" to the mathematically inclined are anything but to a large proportion of children. Many have a decentish knowledge of their "times tables" (or can count on their fingers fast enough to hide it ) but struggle to generalise in the way the OP's daughter did to answer unknown sums by splitting one number into two, and the whole process of "doing sums with letters" is entirely mystifying to them. Some of them can learn tricks to cope with this next level too (multiplying brackets, dividing fractions etc etc) but still fail to grasp the underlying concepts. Would be interested to hear Guest55's thoughts on whether the latest fashions in Primary maths (Mastery? ) are leading to any improvements in deeper understanding in those arriving in Year 7

Guest55 I've just had a chance to read your answer properly. I've never thought of him breaking down the brackets like you suggested. That's brilliant! I think that might help him to *see* it!

That's the way I think it's best taught ....

I am VERY anti going back to the traditional computation methods and mental maths is going backwards I'm afraid. Good schools have always taught problem solving and there's a lot of 'mystique' around mastery [it's just good teaching ie applying what you are learning] - just don't say 'textbooks' and 'Shanghai' to me or I might explode. The Chinese envy our problem solving so why we are getting fixated with their teaching baffles me.

Rant over - sorry

First of all, don't panic too much. I was flabbergasted when, in year 8, my daughter told me that everyone in the class bar 1 (and this is superselective grammar) got (x-7) all squared (sorry I cannot do the little to the power 2 symbol from here) wrong --- they all put x squared - 49 was the answer. There was lots that like that was a bit sloppy I thought, but the understanding was there. Just not enough consolidation for when tired or under pressure to do it correctly.

But they had rushed through a load of maths very fast and not done much at all in the way of practice exercises at home or at school. Also, no text book to do any practice from at home, and at that point in time, never much maths homework.

Bought the text book they use in lessons; when vague homework came home just before big tests like "revise this list of topics" it was invaluable for digging out some relevant questions. Marks improved massively with not much work at all. Top set this year and not shocking me with the silly stuff that was going on last year -- different teacher too.

Sounds unlikely from what you are saying that this is an "understanding" thing as it's easy enough for anyone of moderate intelligence to be taught to multiply out brackets like that as long as the lessons are not confusing.

Guest is on it so you don't need my maths input but I wouldn't be happy about regularly missing that much lesson time. If he was a natural mathematician then he could probably make up what is missed by himself but if like the majority he needs things explained then I wouldn't do it.