US CODE - TITLE 37 > CHAPTER 3 > § 203
(c) A cadet at the United States Military Academy, the United States Air Force Academy, or the Coast Guard Academy, or a midshipman at the United States Naval Academy, is entitled to monthly cadet pay, or midshipman pay, at the monthly rate equal to 35 percent of the basic pay of a commissioned officer in the pay grade O–1 with less than two years of service.
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That's equivalent to an E-5 with 8 years of service under their belt. That's the "high time in grade" average for making E-5 in the Army. Different for the other services though. For cadets, I've always told folks to select the pay grade of E-5.
