In my practical experience, in schools with mixed-year classes 9and a limnited number of classrooms) two things seem to be taken into account:
- Number of children in each year group AND
- Total number of children in the school, and to an extent how they are distibuted in mixed age classes.
So my old school (mixed age classes, PAN of 20) some year groups had admitted over PAN - highly mobile population, especially Travellers, who sought us out as 'their school', very high number of children being admitted at points other than reception. Other groups were at or slightly under PAN. As long as the total number of children was under the total capacity, because we could to an extent flex the mixing of classes, children tended to be admitted even if it took some year groups over PAN. Where it was starting to cause a problem was when even more children applied, and applied in year groups where we were under PAN BUT the 'slack' had been taken up through children over PAN from a neighbouring year group, taking classes over 30 (for Reception - Y2) and over the safe capacity of some seriously tiny classrooms in KS2.
The school that you are applying to may have a similar issue, in that they may have no space to split the mixed year class down further because the neighbouring year classes are absolutely full, even if the PAN is technically not being exceeded (the fact that y5 is being split between two classes suggests that this might be the case if e.g. the Y6 group is very large) It will be harder to argue balance of prejudice in that case than it would be e.g. if the Y5/6 class is quite small and more Y5 pupils could easily be accommodated there, freeing up space for admitting Y3 up to PAN.
17, btw, is a really odd number. You need to find out about the Y5 / Y6 class and how / why Y5 is split
e.g. 17 Y6 + 13 Y5 = Y5/6 class of 30
4 Y5 + 15 Y4 + 15 Y3 = Y3/4/5 class of 34
However it may be:
15 Y6 + 10 Y5
5 Y5 + 14 Y4 + 15 Y3
in which case there would be scope to move more Y5s into the Y6 classroom IYSWIM.
As a teacher and a parent, btw (and i have mostly taught in mixed year classes), I would say that such a highly mixed class is NOT great, especially if it is big, and you may well be better off in the larger school anyway, particularly if your child is of an ability away from the average. A 2 year mix is hard, but possible, though it needs better teaching than an equivalent single year year group to enable all children to make maximum progress. A 3 year mix is VERY hard, as even if the Y5s are split on ability, they have different needs (and if they are split on ability, those Y5s may in fact need more help and so may be even harder to teach in a very mixed age class.
DS (ASD traits, history of selective mutism) moved from a small school to a BIG school at the end of Y1. Best thing we ever did for him.
Have they ever operated with more classes?