Oh, I wouldn't let myself be put off by one unhappy, unhelpful person who answered a phonecall.
I do understand the part about foreign children and gymnasium, and would like to try to provide some background.
The system here is designed so that especially the last two or so years of primary school are core to deciding whether a child either gets into the academic stream (gymnasium) or goes to secondary school. In Switzerland, both routes are considered fine. This is because we have an excellent post-school system of apprenticeships (three or four years parallel school and work) and someone so qualified can go on to practice in their line of work, earn a living wage, and have a fine life.
Unfortunately, the education authorities and staff sometimes come under huge pressure from parents who don't understand this system, who believe (based on their knowledge from the other countries from which they have come, and perhaps the more so if the parents themselves are academics) and who, as a result, sometimes get upset if their child's teachers do not support the child's going to gymnasium. This pressure happens over and over because not all parents are willing or able to put in the effort YOU are now properly making, to try to understand how things work here, and to consider many options about what could be best for the child.
This is common. Not every local school has the full integration class. Therefore, the various schools from the area pool the foreign-language children into one central integration class. 30 minutes by bus is not considered unusual, here, and children quickly learn how the routes work and where to change bus.
The reason the system tends to work is because it is individual. In those classes, it's not just language, language, language but a general assessment of the child's abilities and current level, always with the aim of helping the child to need the integration class less and less and to be increasingly be able to fit into the regular, local school.
For example, a child may be advanced (relative to the Swiss system) in maths or music, but not be able to demonstrate that immediately, for lack of vocabulary in the local language. The integration class aims to discern this. On the other hand, such an integration class can help to identify and make up deficits (relative to the Swiss system) which could be in any subject, but especially history, geography or matters related to social contexts. This latter, particularly, could perhaps be of advantage to your child, if he's a bit shy.