At what rank should Soldiers be exempt from organized PT?

Never

There isn’t a rank that should be exempted. The standards adjusted for age and disability (especially combat related)...yes.
Rank...NEVER!

If E-9s and Warrants (all mine did) have to pass the test, so should the Flag officers. In fact one of my CWO4s routinely got outstanding scores expected of younger sailors. Always had him set the pace for me until the last 1/4 mile then he rocketed off.

In some respects, I think the Service Secretaries might do well to participate alongside their Branch service members.

Now for a real pipe dream...why not the House and Senate Armed Services Committees?? Even in a wheelchair, just so they meet the ones for whom they keep reducing cost of living adjustments, amongst other things. Time spent might keep them from considering idiotic legislation for at least a few hours twice a year.

Just imagine!!!

When I was AD at Fort Jackson under USAG HHD, SFC and above were not required to attend organized PT. In the USAR, it was every single PAX.

I think E7 and above is fine, depending on the organization, with exceptions made for those who fail APFT and/or height/weight.

And if the Garrison or Post Commander designate group PT, then that's 100% pax.

NONE!! No one is above doing organized PT and if they think they are, they are not a team player or a team builder!!

As a Master Fitness trainer (P5) I knew it was especially important for all senior leadership take part in organized PT. Leading by example is extremely important to the morale of our soldiers.

Last I knew, every Soldier must take and hopefully pass a PT test twice annually. No Soldier, to include officers, are exempt from PT.
Company, Battalion, Brigade leadership usually administer PT. Therefore feel at times they do not have to participate and delegate responsibility.
Leading by example should be at a premium when it comes to PT, yes this should include senior officers as well.

After they retire

I can see being released from organized PT to perform their own if they have achieved a passing score in XX months. Have them show up for the formation and when the squadron pt starts they would conduct their own routine. It is working for them to maintain standards. Not everyone do the same exercises or gains benefits from them. Allow the more fit individuals to do their own thing after formation but still require them to show for the formation.

when they pin on their 5th star

When ypu outrank the person ordering the organized PT. But then it becomes an 'example' thing and that would depend on what kind of leader you wish to be.