This was not reported anywhere else that I can see.
Putting the pieces together, here is what happened:
UNRWA, under pressure from Western nations that have concerns about the bias in its teaching materials, added what it euphemistically called "enrichment materials" to blunt some of the more egregious anti-Israel and antisemitic lies in the official Palestinian curriculum that violates UN standards.
So for example, the official PA textbooks ask fourth graders about malnutrition and "martyrdom" of Palestinian prisoners in Israel. But the enrichment materials ask students instead to research malnutrition more generally on the Internet.
A lesson on air pollution said that one example was Israeli smokebombs in Gaza. The added material changed the example to forest fires.
Teachers complained about the modifications to the curriculum, and UNRWA threatened to fire anyone who did not comply, according to the official Wafa news agency.
This news was published on November 9, two days before the riots.
The Hamas site says that after the riots, concerned parents met with UNRWA officials and UNRWA agreed that schools will be allowed to hold "national events" that were going to be curtailed. It's not clear to me if this is referring to a separate UNRWA edict to curtail school activities that were anti-Israel and antisemitic (as we've seen in the past) or if this is an oblique way of referring to the curriculum changes. They certainly seem to be related.
UNRWA caved to the threats and violence, which almost certainly were sparked by the parents and teachers themselves.
But no one reported on the riots to begin with, since this is Gaza and the hundreds of reporters there aren't interested in reporting news that is too uncomfortable. Only after the agreement where UNRWA gave in to threats and violence - the desired outcome - was this mentioned in passing as a safety issue.
The idea that police would investigate and arrest people throwing firebombs at schools in Gaza is simply absurd, when the Hamas government supports the goals of the firebombers.