Are art instruction schools that I see about on tv the real deal or a scam?

I love to draw, and I would love to learn more about sketching and painting, And I always see these commercials on tv for art instruction schools where they mail you the lessons and supplies and you get to take a test and you get in for free, and I was wondering if they are any good, or just a scam. Not just the test itself, but the class in general.