However, the real answer is that these kids are earning an Occupational Diploma -- not an academic diploma like most kids earn.
I see what you're saying, but what's to stop Nike from offering an "occupational diploma in shoe stitching"?
Well, I doubt Nike'd be granted accreditation by the state Department of Instruction. Plus I doubt these kids'd have the mental dexterity to run a sewing machine and turn out shoes at a fast rate.
You don't have to approve of it, but we're talking about a group of kids who will never be able to learn language, math and science like other students -- yet the law requires that they are afforded an appropriate public education. Thus, these kids learn self-care skills, learn to count change, learn to cook and clean, etc. The "jobs" they've done over the years have included baking cookies for the school cafeteria, sorting and folding donated clothing at the Salvation Army, and cleaning the firehouse once a week. They learn a variety of skills appropriate to their mental abilities.
They also do a whole lot of fun things that our mainstream students don't: They go out to fast food restaurants, where they go through the steps of enjoying a meal without their families: They order, pay, choose a seat, and clean up at the end. They go bowling, they take swim lessons, they visit the Cosmetology classes to have their hair and nails done, they go to the movies, they go to school band concerts. They do LOTS of fun things, and their coffee and lunch business pays for this (because many of their families aren't able).
Whether you agree or disagree, these kids are getting some positive lessons -- on their level -- and they leave school with an Occupational Diploma, which tells an employer they're capable of doing simple jobs.