If I did nothing but collect and quantify and evaluate statistics of each football player in high school across the country, by city, then state, I probably could put together a list of kids and star rankings where by the end result of 5, 4, and 3 stars at the end of 3 years in college, my picks would probably mirror and be equal to any of these sites.
Kid kills it in high school, regardless of competition, the chances of him succeeding are greater than kids with less off the page stats. Less of the stats, 3* down. All state lists of players, maybe 1-2 5 stars(easiest group to see physical talent and God given ability to be great, minus the "life" affect once kid steps on campus). Next groupings of 4 stars, all city kids, second teamers, then abundancy of 3 star, the honorable mentions. High school coaches and state wide awareness of players is already out there. Then compare local and regional competition, then state competition, compare players from states versus others at same expected projected positions, then adjust a little for players.
All in all the job kind of does itself for you.........there will be hits and misses, but, probability of equal or greater success rates shouldn't be worse than any of these sites, by doing nothing more than stats put up, and local and state newspapers of their lists of top performers and coaches polls and lists of players all state, city, division/conference awards and accolades. Not even watched any film on any kid yet.
And, as the kicker, we are only going off of one thing, playing football........and missing out on the hundred other variables that each kid will have to wade through, fight off, avoid, over come during their college career. The intangibles and important things, like mental make up, conviction, work ethic, time management, compartmentalizing college life, sex life, study habits, determination, attitude, social graces and reactions in social situations, competitiveness, learning and retention, injury proneness or not, rehab, and keep running down life's list of what will be faced for each player in college to make it to the peak of their ability.
Racket.