@mrhorsetwat often it is both the parents and the teachers being bad, not just one or the other. But usually the parents are the bigger problem. Some parents think that they don't have to do anything other than just hand them off to the teachers and take no role in their education.
These days, it would be foolish to assume that your child is learning properly, especially since teachers are usually the least intelligent among the "educated" (see: grades and test scores of Education majors).