Can a teacher with a class of 30 kids really differentiate?

[eastereggfeaster]

Trying to decide between a school with 30 kids and 1 teacher plus assistant in the class and a school with 20 kids and 1 teacher plus two assistants.

Lots of other issues but fundamentally I would like to know whether a teacher in a class of 30 can differentiate if a child is ahead or behind of 'average'.

I would rather my children were in a class of 20 rather than 28 (as is the case with DS) as I think this would enable the teacher to give them more attention.

Nevertheless DS has had 2 very good teachers (1 not so good) and has made very good academic progress.

I think quality of the teaching staff is as important as the class size in a given school.