Complex sentence: So-called "Basic" schools teach Years 1 to 9, as Year 9 is considered to be a decent level of schooling for the majority of children; however, schooling is only free up to Year 7 and most children drop out then.
Split into simpler sentences: So-called "Basic schools" teach years one to nine, as year nine is considered to be a decent level of schooling for the majority of children. However, schooling is only free up to year seven and most children drop out then.