It's always worth the money - this is actually the second time I've been to one of the schools.
The principals aren't different (that whole science thing)...it is the personal attention and prioritization of what you need to do first, then second, etc. to get better. I always leave hitting it better than I ever have with a great understanding of what I need to do and continue to do to get better. The guys are generous with their time and will have you hitting it better within 10 balls...guaranteed ;).
If you have the opportunity to attend a school...do it. It will change the trajectory of your learning curve immediately.
I'm a lower hcp player...was a poor ballstriker that could score a little to keep it in the 70's. The day after my first school with Andy in NJ last August, I hit 16 green, 2 fringes, 12 fairways, and shot 69 on a very difficult golf course. Individual results may vary? No, you will hit it better guaranteed.