That's one example. It's estimated between 10-15% of all rockets Hamas have attempted to launch into Israel have fallen short and landed in Gaza, which equates to thousands. It's impossible to know many Palestinians have been killed by these, because unsurprisingly Hamas aren't keeping record of it, but instead adding those deaths onto the tally we see reported daily. And, again, that tally doesn't differentiate between Hamas militants and civilians.
Israel are entitled to bomb schools, hospitals etc if they are being used by the enemy for military purposes. It's looking like this whole situation will be reviewed by the ICJ. When the time comes, if Israel can produce evidence of the sites you mentioned being used by the enemy for military purposes, or to gain a military advantage, they will be cleared of wrongdoing.
Regardless of which side of the issue you fall though, the biggest sticking point is proving intent. If you believe Israel are intentionally starving a civilian population for example, can it be proven? Israel will almost certainly say any delay to the process of getting aid into Gaza was a matter of security, not an unwillingness to feed civilians. Unless this can be proven otherwise with actual proof, not just people's opinions, then it's a non-starter in international courts.
