Of course socialist schools are going to promote socialism. The only mistake the classroom bureaucrat made was getting caught by giving the package to a kid whose father bothered to see what was in it.
Of course, if the father wasn’t having his lifestyle subsidized by participating in the nation’s biggest “entitlement” program he might find a capitalist school is less likely to promote socialism than a government school is.
Parents, educate your children. Inform them and empower them.