Education is a team sport. The parents ought to be held equally if not MORE accountable.
Ah yes, we shouldn't settle for anything less than perfection.
For any set of students+parents, some teachers will do better than others. Why should kids with lousy parents have to settle for lousy teachers as well?
Part of being a good teacher is managing mediocre parents. Why should kids with mediocre parents have to settle for lousy teachers?
The reality is that the home you come from is hugely important, but there isn't a lot they can _do_ about that -- and certainly not in the short term. Firing the teachers may be only modestly effective, but it's achievable.