Removing Sand from blacktop

Anything you do to dissolve the paint or with a pressure washer will also remove some asphalt.

I'd vote for a good pressure washer, as tar can be messy stuff since it too will probably dissolve under the action of paint stripper. Rent one if necessary, BEFORE the paint has had time to harden is best.

Once that is done, however, you will still be left with an image of what you stripped off. So I'd next take the opportunity to apply some blacktop sealer to the entire driveway.

Finally, ensure that the kids who did it will not repeat the action. Their paying for the work will help in that respect. If they are required to help do the repair itself, that would be best.

There are lots of concrete cleaning products on the market, but I have had good luck with a 1 gallon solution of 1/4 bleach, 1 cup TSP and 3/4 water. Assuming you are talking about a driveway or garage floor, I would pressure wash the area first to get off the surface crud, then lay on some of the solution and let it set 5 mins or so. Scrub it down with a stiff broom and power wash again. Repeat this as necessary.
As a last resort, you can also use some muriatic acid, but test a small area first to be sure it doesn't effect the color too much.