Computer training option 1: Go to college
When I started at my local university there were several high school students attending classes through various programs. Junior colleges and state schools have free and reduced price classes for high schools who want to attend classes part-time. Your brother can also take classes full time at the local junior college by getting his GED. Classes from the Management Information Systems department (a.k.a. Computer Information Systems) will teach the basic computer usage skills you have requested.
Computer training option 2: Get certification
The problem with homeschooling is at the end of an excellent education you have no real way of proving your computer skills. After all, the SATs do not test your skills with Excell. Getting Microsoft or some other certificate would be an excellent way of to test your brother’s skills and have a curriculum to follow.
Does anyone have suggestions for what certificates a high school student should get?
Computer programming option 1: Java
The Advanced Placement tests that give high school students college credit assume the student knows Java. I suggest an online introduction to programming college course, however these are more often taught in Visual Basic or C rather than Java.
Computer programming option 2: Ruby
The Ruby scripting language would give you brother an easier starting point that Python or Java while still teaching object oriented programming concepts. The best part is that he can use “Why's (poignant) Guide to Ruby,” a short simple introduction to the language written by an insane man. I think the text would be very appealing to a high school student. Please check it out and enjoy the soundtrack.
HTML version: http://mislav.uniqpath.com/poignant-guide/