Time at the academy does not equal time in service (it doesn't count toward your retirement in calculating the number of years served). From the office of SecDef:
It does count as federal service.
It is considered Active Duty:
37 USC 101(18) states, "The term 'active duty' means full-time duty in the active service of a uniformed service, and includes full-time training duty, annual training duty, full-time National Guard duty, and attendance, while in the active service, at a school designated as a service school by law or by the Secretary concerned."
38 USC 101(b)(21) states, "The term 'active duty' means service as a cadet at the United States Military, Air Force, or Coast Guard Academy, or as a midshipman at the United States Naval Academy."
38 USC 1965(1)(d) states, "The term 'active duty' means full-time duty as a cadet or midshipman at the United States Military Academy, United States Naval Academy, United States Air Force Academy, or the United States Coast Guard Academy."
It's probably just not well known since most active duty aren't exposed to cadets or midshipmen on a regular basis.
Well there we go. according to those statutes, time in an academy is considered active duty. Interesting. So I am confused how the link at the beginning says it does NOT count.....
Following the link all it does state is that it does not count towards your retirement time credit.