Chiming in a little late. Actually, a lot late. Oh well. I'm just going +1 everyone else's response except the one quoted below. It's too late for Crispin, but I'm going to dissect their post a bit and maybe it will provide further help / insight into POC issues (I'm not white, and I'm not black, nor brown, but in America (and the UK) would definitely be POC).

Quote Originally Posted by Crispin View Post
You shouldn't worry about things like that.
Yes, you should worry about these things. It's called being socially aware and sensitive to issues other than one's own immediate circle of problems and solutions. No group should ever be invalidated or dismissed because an opinion states so.

There are people who will call you a racist if the criminals are poc, but also if you feature more whites in order to make them the criminals.
Actually, for those of us who are POC (very large population, and worldwide), IMO, this is offensive. Why? Because what I'm getting from this statement is that it is telling people that it's okay to write POCs are criminals, but if adding more white people as criminals, then it would be detrimental to white people.

There are a group of people for whom "being outraged" is now a life pursuit. And if someone wants to be outraged, there is literally nothing you can do to keep that from happening. They'll find an excuse. So don't write for them, ever. Write the story you want. Do it well, and you will gain fans. Real ones.
Surprisingly, or not: I actually agree with this. But my POV would be to write for yourself first (with your potential audience in the background as you write). You can always edit.

As for your premise, I think it sounds great. A teacher working in the inner city and solving crime would be a unique twist on the usual story of the put-upon teacher in the inner city.
Another agreement here.

Should the criminals be mostly poc? In that setting, how could they be anything else?
Wow, does this come from a place of privilege! POCs are as far ranging in law-abiding to criminal as white people. And in the States, the current trend (according to the news -- TVB, BBC, CNN) appears to be more white people committing racism / other crimes. But they don't get as much air time as POCs. And the headlines in the papers are biased towards white people. (I need to add a citation here -- a bit later when I dig out the links again.)

It's not even about racism,
It is about racism. "POC criminals" vs "white heroes"?

it's about what makes sense.
Yes, it is about what makes sense; but it's also about due diligence and making sure that the story told is the one that needs to be written. Not all POCs are criminals, just as not all white people are racist.

A story about the inner city where somehow the gangs are full of white kids in polo shirts? It's so out of touch with reality that people would simply be confused. Stick with what you've got. And, as I said, do not worry about the outrage mob.They're loud, but small, meaningless, and certainly disingenuous.
I'm ignoring this last paragraph.

If you must make your MC white and POCs the criminals, then do so; it's your story after all. But as Cornflake said, selling the story is another matter.

Eesh! I feel a rant coming on. Bowing out for now!

Good luck!