It's definitely not the responsibility of teachers to enforce rules on behalf of the parent. Their obligation is to enforce school rules (which should suffice on the discipline side) and do their best to educate students. In terms of keeping parents up to date on the progress of younger children, that's ultimately going to be a judgment call, but the way the kid expresses themselves isn't something particularly important. In general, a teacher would be talking about the successes achieved and challenges faced by the child.
That's my opinion as a part-time college teacher, anyway.
