Your right about this. The children are comming in as neutral, usually aloof, parties. Some will want to educate them to their potential. Some will want to fool them. Some will want to protect them from vulgarity, and some will want them to accept and practice vulgarity.
Was the bus driver tying to fool them? Was she trying to get them to accept or practice vulgarity?
By what authority does she decide how and when those children will learn such things, and thereby usurp the role of parent. By what right does she presume to know better than the parent how to raise those children?