So your definition of mandatory is “most of the time”?
Nope, but opt out works better for affluent families, the poor folks are who most of this stuff is aimed at. Sort of like Congress passing laws that they are exempt from.
If they wanted to make something optional, they would do Opt In. This is exactly how they get kids herded into Sexual Indoctrination classes. Students are given notes to take home for parents to opt out, student throws paper away, student ends up in a Homoerotic class.
Wise up, it happens all the time, I know from experience.