No, while cadets are at the academy, they are not considered active duty. Their service does not start until they graduate. You must be a very proud parent.
Please confirm your sources. Cadets at Military Academies are considered active Duty.
https://www.law.cornell.edu/uscode/text/38/1965
https://sgp.fas.org/crs/natsec/IF11788.pdf
This may also be helpful
https://ttlc.intuit.com/community/taxes/discussion/how-do-i-change-my-military-pay-grade/00/967673
We have generally been telling/suggesting to them select as E4 or E5 in the software selections.....about what they would be if they dropped after sophomore year. but not exactly sure of their exact paygrade.
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.