My son let his car overheat and it shut off.

Do a cylinder compression test. If the cylinders can't pull vacuum or make pressure, you may be looking at a major overhaul? If it cranks good but won't start, have a helper crank it while visually check for spark at the spark plugs. If you have spark everywhere, use a gage and check fuel pressure.

All the fluids check out ok? Tranny-- engine oil-- antifreeze. Why did it overheat?