They are preventing the private schools from being destroyed through the voucher systems.  I was training to be a Biology teacher before I decided to go to med-school instead. I got through 1 semester of student teaching my sophomore year and immediately changed my major after a week of observations. Public education is absolutely fucked. In some places it's so bad, they can't find warm adult bodies to be legally responsible for the children, let alone actual certified teachers.  At first I though unions were just parasites. Turns out the teachers unions are the only ones fighting for student accountability and suspending the violent animals who come in and throw chairs at teachers and students.