HS players are the hardest to project, but can have the highest upside. At one point earlier this year, on MLB.com's top 100 prospect list you had to go down to at least #17 before you found a player who was drafted out of college. The top 16 were drafted out of HS or an international FA signed at age 16.
So take a bunch of HS players, throw them up against the wall, and see who sticks. That's kind of what they did with Knoth, Bitonti, and Pratt (and to a lesser extent, Birchard, as he was still 19 on draft day).