hi darenet
this is not a swiss person's answer but i'm also reading on the topic as my son just started kindergarten and i get so confused when people speak about all the different schools available...and the course through the school system seems a bit convoluted, i attended, primary school and then high school and then went to university, here it the same journey has many names?!?
according to this article http://www.ag.ch/aargauservices/shar...are_e_(3b).pdf
9 years of school is 'obligatory' so to answer your question, government requires children to go to school until about 16.
i hope that makes sense and at least partly answers your question? each kanton (and there are something like 27 of them) has their own system and no cantonal or federal exams are written, so the 'level' in a class is determined by the teacher...
sd
ps. good explanation of zurich canton and also your elementary school question is answered - you're right! http://www.about.ch/education/index.html