There can be no debate that overcrowding means less time a teacher can interact with each student or even learn where an individual student could be deficient. That's undebatable.
One teacher can't maintain control of the classroom. When I was in school spit-wads or rubber bands were how we annoyed people when the teachers back was turned. I remember one fellow student throwing a paper airplane that flew and stuck into the hair on the side of the substitute teacher's head - that set her off.
But from what I see there is no shortage of pregnant Dominicans also helping over crowd the schools.
Solution of course is to build more schools, and I see some being built nearby but as long as you staff it with poor quality and disinterested teachers, even less crowded schools won't give children a decent education.
This is why private schools do well in DR.
The parents know the public schools are little more than walled babysitting services. But only those with money are able to get their children help in private schools. And I see many Haitians working their tails off also putting their children in private schools too. I know several Haitians doing that.
Overcrowded schools & alternate private schools for wealthier families is a world wide phenomenon, so at least DR is on par in that regard.