Class size

[Vikster23]

My son is currently in a mixed yr3/4 class of 35 pupils. They have a class teacher and a TA that is shared with the other yr3/4 class.
Whilst I recognise that there is no minimum class size at ks2 are there any recommendations for pupil adult ratio or classroom size.

It does sound like a large class especially for a composite. I'm a teacher in Scotland where max size in primary is 32 and only 25 if it's a composite. However I would say that the impact of class size mostly depends on the class and how many differing "needs" there are in the class. If they're all fairly average and lovely children who speak English then it shouldn't be too bad.
Compare with a class of 20 with a stretch of abilities (including low and gifted/talented), 10 different first languages with new arrivals at different times of the year, some children with dyslexia, ASD, visual or hearing difficulties, children from broken homes, emotional and behavioural difficulties.

The simple answer is that there is no maximum in theory. The reality is going to be around how large the room is, so how many pupils could be accommodated in the room and to some extent what say the teachers in the school have on maximum class size.
If the room is typical of 50 to 60 sq metres then I would not at an appeal hearing been keen on going about 33 unless there were very very good reasons to admit. So in that context 35 does seem to be getting quiet big.

My DS was in a class of 35 in year 3 (down to 34 now in year 6). DD is in a year 3/4 class with either 34 or 35. Hers will go down next year though as her year 4 is about 28 - year 3 has over 40 in it. DS has been fine with this size of class through ks2 - shall wait and see about DD. Am slightly wondering what will happen when she's in year 6 - am guessing mixed year 5/6 classes and bigger ones again.

This has always made me cross. Infant class sizes are (rightly) restricted to thirty. Secondary schools seem to have a fit of the vapours if any of their groups approach the high twenties, but poor old KS2 has to cope with classes of well over thirty.