Evelien wrote:Where does middle school begin and where does it end..? I'm not familiar with the American system

Here we have 'basisschool' (primary school) where kids go from the age of 4 till the age of 12. Then they go to 'voortgezet onderwijs' (high school) until they're at least 16 (medium level), until they're 17 (higher level) or 18 (preparing them for university).
It can be a little weird because there is no 'standard' system. Each state and indeed different school districts within the state can divide the school up in various ways. In NY State, kids start with Kindergarten at 5 years old (although some go to Preschool), but actually they aren't required to go to school until they are 6 (but that almost never happens). Elementary is PreK-6th grades (4-12 years old), some districts will have a 'middle school' which might cover 5-8th grades. Junior high is usually 7-8th or 7-9th grades (12-15 years) and then high school 9-12 or 10-12 grades (15-18ish).
It really depends on the individual districts facilities and what they have room/buildings for. I just left a small district where the elementary building and the high school were connected by the pool and a hallway. I was in the 'high school', but the 4th and 5th grades would come over to have art class with me. The school I'm going into is so small (private catholic) that the entire school PreK-12 is in one building. The largest district I taught for had 7 elementary schools (PreK-5), 2 middle schools (6-8), and two high schools (9-12).