What is my 6 year olds shcool teaching him?

yesterday I got a call from my son's school informing me that he and one of his friends had plugged a toilet so bad with papper towl that they had to call in a plumber. I talked to him on the phone about it and then he went back to cl. When I went to pick him Up I asked his teacher what his Punishment would be.She said that the fact that he had to call me and write a letter to the janitor to say sorry was good enough.I'm sorry What? So I went to talk to the principle and suggest that he do some stuff around the school to make up for it.She told me that that was to harsh and he had already been punished. And that I should not be so anry with him. So when is it not to harsh ? when he and his little buddies break a window because they think it's funny to throw rocks at them? I think his school is sending him the wrong message about this kind of behaviour. What do you as a parent think of this attitude from the school?