Can your chain of command pull you from your college classes if you fail an ACFT and come under a flag?

If you're in online school and your tuition is already paid for, what you do after work is your business. Your Commander can't disenroll from a college class. However, once you are flagged you are no longer eligible for TA. If you're going to class during the work day, your Commander has 100% ability to control where you spend your work hours

Now that you are flagged, you should read the whole reg, it's only 34 pages.
AR 600–8–2 • 5 April 2021
Chapter 3 Prohibitions and Retention of Flagged Personnel
3–1. Actions prohibited by a Flag
f. Attendance at military or civilian schools. The waiver approval authority for attendance at military or civilian schools is the DCS, G–3/5/7 (DAMO–TR).
(3) Civilian schools are defined as those post-secondary and technical institutions in which a Soldier takes, either on a full- or part-time basis, courses that were fully or partially funded by the Army. This does not apply to self-funded education courses taken at civilian schools.

If the college classes are funded at all by the Army, or if the classes are during the duty day, that is a favorable personnel action that is now suspended.
If you are paying 100% of the tuition an fees out of pocket, and the classes are after duty, that is not a favorable personnel action.

As in, you're taking online college courses and are now flagged? I'm not aware they can pull you from classes, however....the flag will stop you from getting TA, though.