Hey There @methusalem,
Not surer of the system you have within your school, but with our kids with some of the schools they have attended, school teams will only pick kids that have be on teams outside of school and cherry pick the best of the best.
Which in turn makes kids not want to join Extracurricular activity's where they miss out learning if they like it or not, or only join activity's were they will teach how to do that activity due to low number of kids not making a full team to represent the school.