Not trying to 'defend' islam, but I think that for schools which are majority muslim it may make sense to close schools on days when most of the student body will not come into school. This is why some schools give the Jewish holidays off in majority Jewish neighborhoods. It saves a lot of money for the school system to avoid having to pay for teachers and heating rooms which don't have students in them. I don't think it is a way of honoring the religion itself, although I may be wrong.