I think it really, really depends on the school and how it supports the children. Here's a comparison from a different country (Scotland, independent sector):
The Pre-Prep is nursery (3+) and P1-P3 (age at start of P1 is 4.5-5.5, so this is 4-7yos) in one building, with one teacher for almost everything and lots of play built in;
The Prep, or Upper School, P4-P8bis (age 7-13yos) in a collection of other buildings, with a different teacher for almost every subject, a timetable, going round the school for different lessons prompted by bells, school day running 8.30am-6pm. Yes, all that for 7yos; it takes them a little getting used to, but the teachers are supportive and they are fine! (It is a small school, 300 in all, which helps - none of the rooms are more than 5 minutes walk, they get to know most of the other students by sight.)
