I'm sure being comfortable is very important for the pupils. If they're hungry, tired through lack of sufficient sleep, cold (I've sat through several power cuts with no heating in the school and the children in their coats. They'd have closed the school nowadays, of course) or even unhappy due to bad conditions/abuse at home, then no-one can expect them to do their best and achieve all of which they're capable.
My husband sat in class for hours with hunger gnawing his insides as he often ate only every couple of days.

There can't be many students today in the West who have these problems. However, modern times bring their own difficulties. I imagine many teenagers have angst due to nasty texts, social media bullying and remarks about their appearance etc. It would need to be a very wise and stable society that produced excellent educational results in the young.

I'm going to sound like a real old gal now, but honestly, just after the War, where I lived we had most things necessary for a very good education. Discipline, simple but nourishing food, stable home life, lots of fresh air and exercise, no internet or TV, dedicated teachers, parental support of the school and high expectations of our capabilities. Most of my schoolmates did very well under these conditions. Slippers didn't enter the equation!