Kinda common sense. Let me clarify one thing first though, Im not saying that an off the street hire cannot make an excellent controller. So in essence the people going to the academy after the last hire are almost all off the street hires, this means few CTI and military hires. CTI and military hires have a pass rate over 90% and the academy is fairly easy for them (generally speaking). An OTS who has very little experience in aviation has a much higher chance of failing out of the academy. I can't give you numbers but I would expect a much higher turnover in the academy.
The academy is a serious program. 2 months of fairly rigorous and fast paced training. People without experience are going to be less successful.
