Re: Academy vs. Civilian college attrition: Not sure what to add by way of opinion, but the data sometimes help.
From the website collegedata.com, which pulls from IPEDS, the following are the rates of Freshman Return, and the 4 Yr. graduation rate for colleges. I decided to sample by starting at US News #19, Notre Dame, skipping 5 places on the list, up through #40. I listed only Private schools, and none that are huge in size. Next are very small Liberal Arts colleges, starting at #10, and again skipping every 5 on the rank order.
It doesn't appear from a distance that the attrition shown in these data at the Academies is notably different from other Universities and Colleges with high admissions standards and rigorous academics... but the reasons are probably very different. For one, these colleges are quite expensive, and it is not uncommon for a student to need to leave because the financial situation at home changes and the family cannot continue even with Financial Aid and Merit money. However, if we go by the seemingly common knowlege that around 20% of first day reports at the three Academies do not graduate, then it does appear to me that the Academies suffer greater attrition than other colleges that are academic peers. If attendance were not almost free, I wonder what he attrition rates would be?
I suspect the data from USNA are a little off... or maybe they don't count the I-day reports who leave during Plebe summer before formal academic instruciton begins. I am certain that far more than 2% of the students arriving at I-Day are not present the first day of sophomore year. My guess would be that around 10% leave prior to Youngster year. I am also relatively certain that about 20 who report on I-Day do not graduate. So these data are... suspect but a starting point.
Here are those data:
School // Freshman return rate // 4 Yr. Graduation rate
School // 1 Yr // 4 Yr
USMA // 95 // 83
USNA // 98 // 88
USAFA // 89 // 78
Notre Dame // 98 // 90
Wake Forest // 94 // 83
Boston Col // 95 // 88
Rochester // 96 // 69
Lehigh // 93 // 77
Haverford // 96 // 87
Vassar // 96 // 90
Bates // 92 // 84
Bryn Mawr // 93 // 80
Holy Cross // 94 // 90