You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Bern

Context:
The Canton of Bern school system provides one year of non-obligatory kindergarten, followed by six years of primary school. This is followed by three years of obligatory lower secondary school where the pupils are separated according to ability and aptitude. Following the lower secondary pupils may attend additional schooling or they may enter an apprenticeship.

Question:
What seperates the children in secondary school?

ability and aptitude