Extrapolating from the HS to College level is definitely more difficult than College to Professional level.
That being said, there are some very strong HS football leagues across the nation and if you are seeing kids from those leagues, there's a strong reason to believe that those that perform well at that level will perform well going forward.
With HS kids, what you are looking for is a combination of natural athletic ability as well as an ability to further develop.
Regarding player development, some coaches are better than others. Pete has a very strong record of player development at both Boise and UW. It's one reason why I never worry too much about TCU recruiting because Patterson's track record at player development is one of the best in the nation. No question this matters as much as anything else. IMO though, the better the base level that the coaches start with, the better the upside IMO.