This is about emotional control, not school issues, but it's still a success that might be useful to someone...
For my DS4's OEs, I now ask him to rate the way he feels on a scale of 1 to 5, where a 1 is "I'm fine" and a 5 is "I will surely die any moment from a broken heart!" Then I have him rate the problem that caused the upset on a scale from 1 to 5. I do this while he's crying, after a meltdown has started. (I know that seems like it would be too late, but it's apparently not.)
It is working like a charm to calm his excessive emotion fast and simply. I suspect the mere act of analyzing his situation distracts him enough to rein his emotions back in, and asking him to compare reality to how he feels about things lets him see the disconnect between the two in a useful way.
He now seems to accept that having a wailing, crying meltdown over where the tongue of his shoe is on his foot is not really appropriate. (That's not to say he has completely stopped crying over it, but he's easy to bring back to calm now!)
That's a BIG step in the right direction!
I confess, I'm pretty proud of myself, because I just thought this up on my own. And it seems to be working amazingly well!

Yay me!
I hope it helps someone else!