In addition to ak's recommendations, you might consider Forsyth Technical Community College (
Home - Forsyth Tech). They offer a construction/carpentry curriculum, and often courses are available for high school students to take at night or during the summer. To my knowledge there is no high school in the area that offers cabinet-making specifically, but if you contact the career center and explain your situation I'm sure they can steer you to the best solution that's available for your son.
Good luck, and if you have any other questions about the Clemmons/Triad area, please ask!