It comes down a lot to your definition of responsibility. Yes, those teachers were adults who could make their own decisions. But sometimes you can make all the decisions that you see as being the best and most informed at the time you make them, and still produce poor outcomes, simply because you don't have the resources or knowledge or ability to do better.
So should we judge the teachers based on how they tried to make decisions in the moment when the author was young, or should we judge them based on the results of their decisions with the knowledge that we have now? I find that quite a hard question to answer definitively, but I do know that I tend to use the former rule for myself and the latter rule for others, which certainly seems quite unfair to me.