Gymnasium entry rate is more closely connected to the socio-economic status / disposable income of the parents in the community than anything else ... as k_and_e says, lots of private/external training.

Also, getting into Gymnasium is not a guarantee of surviving the probation time, in which about a third of entering students are filtered out, nor is completing Gymnasium a guarantee of success in life (nor is it the only path into university, if that's your child's goal).

The Swiss education system has a whole heap of options for students, which can look daunting at first, but allows everyone to find something which suits them.

Fortunately, with children as young as yours, they've got time to sort out what they want well before they get to the end of primary school and have to decide.