If you saw one of your Joes doing this, how would you react?

Before saying ANYTHING_have the facts, because if YOU are wrong-you're butt is in a sling and a young ladies reputation IS damaged!!! What if it's his sister,cousin? Could be a girlfriend, but remember-HAVE FACTS BEFORE ACTING!

4–3. Occasions for wear
a. All-purpose wear. Some versions of the combat uniform are not intended for wear as an all-purpose uniform. The
combat uniform is designed to be worn under body armor.
b. Approved wear. The combat uniform is prescribed for year-round wear for all Soldiers, unless otherwise directed
by the commander. Soldiers may wear the combat uniform off-post, unless prohibited by the commander.
c. Restrictions on wear.
(1) Soldiers may not wear the combat uniform for commercial travel unless authorized IAW paragraph 3–7b through
c, above.
(2) Personnel may not wear the combat uniform in off-post establishments that primarily sell alcohol. If the off-post
establishment sells alcohol and food, Soldiers may not wear the combat uniform if their activities in the establishment
center on the drinking of alcohol.
(3) The combat uniform is not normally considered appropriate for social or official functions off the installation,
such as memorial services, funerals, weddings, inaugurals, patriotic ceremonies, and similar functions.
(4) Commanders may further restrict wear of the combat uniform IAW paragraph 2–6c

That looks like Homecoming pep assembly, prior to the evening of the dance. Clearly it's not a formal occasion, as no cheerleader would attend a dance/formal in their uniform. Cheerleaders in cheer uniforms, a JROTC cadet in uniform, and the rest of the Homecoming court. They probably just found out who was selected for Homecoming Royalty, and took the picture during school. The other three males could be football team members, and were all dressed up (as most teams require) prior to the game.

Your serious. Soldiers, Sailors, Airmen and Marines are on TV in their kids classroom returning from deployment what's the difference. Find thing more contructive todo with your time.................

I'd tell him, next time, wear ASUs, then let it go.

My soldiers knew the proper time and place for uniform wear. It would not have been mine. Now on the Other hand, one disobeyed and was stupid enough to post pictures I would question my leadership and his mentality in a private discussion with his 1st line leader and him and figure out what is going on in order to determine how to prevent future occurrences. But remember we do not know the whole story from just a picture. It could have been a father stopping to pick his child up from school and her and her friends wanted a picture. Do not always assume the worst.

I replied below but from the perspective of the offense being him posting the picture on Facebook. Some did the same but others responded to physically watching it. I don't know Army regs and see Guardsmen and Army Reserves in utilities fairly often in town. I don't know all the various names for BDU's as we simply called them cammies. All others are dress uniforms which for most part are ok in town with some exceptions regarding medals etc. Unless regs have changed since I retired in 98 cammies are not allowed out in town at all. There were with minor exceptions such as going through a drive through window or maybe a quick in/out at convenience store. It would be a whole different animal for this scenario in USMC. Folks definitely know better and it would be dealt with a lot differently. Before I retired there were often stories of senior Marines ripping ear rings out of Marines ears in malls while in civilian attire and so forth because they are not authorized. Not condoning that but just saying that it would never be considered as even marginally acceptable in USMC. Not slamming Army at all, just noting differences in policy. Best Wishes to all.

I was in Army JROTC before entering the Air Force and we always wore ACUs for everything. This looks like a homecoming court at a football game where said JROTC cadet was probably on detail and was required to be in ACUs. When it came down to formal dances we followed the schools dress code for the event. The only exception was the military ball we had every year.
Also while all active duty members must follow the required uniform regulations that is not the case for high school students in JROTC. So honestly, there doesn't seem to be anything wrong with this picture. Just a dude in high school walking his girl for the homecoming court.

Also notice he has no patches, etc. on his uniform and due to positioning you can't tell if he has JROTC rank on or not. I could be completely wrong but I'd give him the benefit of the doubt.

This looks like it came from the high school's nomination assembly. If he was a member of ROTC he would have been required to wear his uniform to school on days that he had ROTC. It may have simply been coincidence that the two events fell on the same day.

In the early 70's a soldier was not allowed off post wearing what was then called fatigues. Only exception was going to/from off base housing with no stops in between. The rules were slightly relaxed when going off post for lunch at fast food places.