And there's also the differences in how death is handled pre-and-post M-Day. spoilers:end of spoilers
When Northstar dies, the kids are counseled and protected as much as possible (even outright lied to, over Dani and Karma's objections), and have ample time to mourn. By contrast, the strikes against the school by the Purifiers are massacres, and one comes right after the other with no time to breathe or absorb the loss.