More than 10,000 teachers, principals or other school staff were assaulted or threatened by students last year, The Post reported Sunday — a 4.5 percent rise over the year before and 11.8 percent over the year before that. Does Mayor Bill de Blasio still think his school discipline policies are working?

Over the three years, these incidents resulted in injury to 8,253 school staff.

It’s surely much worse for the other kids. After all, school staffers are adults.

And teachers believe many incidents never make it into the official data: Pressure is huge to show that safety is improving since de Blasio ordered a mass reduction in suspensions and other “tough love” discipline.

The Department of Education didn’t want the public to hear about these problems: It took 18 months to comply with The Post’s Freedom of Information request for this info — even though any competent bureaucrats who want to know the facts on school safety would have it at their fingertips.

Asked about The Post’s findings, teachers union chief Mike Mulgrew simply talked of his “frustrations” with the failure to make good on contract provisions that mandate safety plans for every school, along with counseling, training and conflict resolution.

Mulgrew, it seems, won’t make a stink as long as the mayor keeps the pay hikes coming. Plus, Team de Blasio may not be doing much for union members’ safety — but it’s protecting the union by doing its best to crush (mostly non-union) charter schools.

To be fair, the union boss isn’t alone. Few other politicians will speak up against de Blasio’s weakening of school discipline, because there’s a racial angle: “Too many” black and Hispanic kids were getting suspended — and never mind if cutting back on suspensions puts mainly other black and Hispanic children in danger.

Thanks to this conspiracy of silence, even September’s student-on-student homicide at the Urban Assembly School for Wildlife Conservation doesn’t have de Blasio reversing course on school discipline. Will it take more deaths to make him rethink?