Two of them show clear sinkholes - indicating pretty strongly that there are Hamas tunnels directly underneath the schools.
This picture is very clear - the pavement doesn't even appear to have been damaged (much?) by an airstrike, it looks like it simply caved in:
Something destroyed a tunnel underneath.
Let's look a little closer:
Here's another that shows an obvious sinkhole that would not look like that if there wasn't an empty space underneath,.
UNRWA has, in the past, condemned Hamas for placing weapons in its schools. But it only does that when the violation is undeniable. It seems unlikely that they will say anything negative to Hamas about this - because, in the end, they are on Hamas' side.