This is not about "good" and "bad" teachers...nor, for that matter..."good" and "bad" parents. The topic of this debate is: "Should unhealthy foods be banned from school?"
It really has nothing to do with teachers, although teachers may become involved. It's not in their contract to be in charge of what goes on in the kitchen, or to determine the meals that will be served in the cafeteria.
So, I really don't understand why teachers have become a part of this discussion...not to mention, denigrated, as they so often (and so casually) are on this site...but, time to move on...
This is definitely something parents should take an interest in, and be proactive about. If they care, they will...it's that simple! No parents are ever left outside the gate...and the school is always a phone call away.
The fact of the matter is, as I mentioned...parents have more power than they realize...they just don't often exercise it! This is why there is what is called a Parent-Teacher Association (P.T.A.). Parents simply need to show up and voice their thoughts and opinions...possibly volunteer, and/or hold an office.
Schools often have committees...for example, a School Leadership Committee...which affords the opportunity for parents to become voting members, or just attend meetings.
They can have an input as to what should be taught in the curriculum, and voice any concerns at all...including, unhealthy foods being served to the children.