Thanks for asking!
That's a very personal question though. It depends on what you are looking for. In @marc's classes you'll learn a lot from basic shapes to anatomy, character design, creature design, robotics and so much more! If you are looking for similar classes to those of a physical art school, you'll get just that but more focused on what really matters to become a great artist at painting, drawing, sculpting, etc!
Personally, I would definitely recommend it! 2000 others have already joined Art School and I've seen great improvement in students that spent a lot of time following these classes regularly.