I took a group lesson from the Hans Hedemann Surf School in Waikiki. The lesson was 2 hours in length, with 30 minutes "dry land" training (how to stand up, etc) and 1.5 hours in the water. This was billed as the "best surf school" on Oahu - but it failed to live up to the hype. Instructors seemed to put minimal effort in teaching you how to catch the waves, sometimes taking off to catch waves of their own. Not any feedback on how to improve your surfing. Also, there were definite "favorites", so while everyone pays the same cost, certain students got preferred treatment.
After the lesson, they show you a few seconds of video with you surfing, and try to get you to buy the DVD (30 bucks!). Again, this is more of the "favorites" and instructors surfing. Cheaper surf schools exist with better instruction. Overall, this "surf school" is not worth the cost. Better yet, get a beach boy to teach you - personalized instruction at half the price!