20 at our school too and as traveller says, they vary number of classes according to kids enrolling. But then, it is a big school so they have flexibility. Also have to say big schools not all bad. we are at one of the biggest state schools in melbourne. It has a great closeknit school community, lots of facilities and full time specialist teachers in music, art, lote, sport. So the classroom teachers get release time to plan programs so they are happier and less stressed. And always having other kids to play with when there are issues inthe playground has alot to be said for it.
i would be very surprised if they can make 77 children go into 3 classes of over 25.