What constitutes being "old school" in the military?

If you were in the Army Air Corps, that was old school.

To me, "old school" is more than having served "way back when." It's a frame of mind when putting the job first (after God and family) meant everything.

I'm so old school we never had PT or yellow shorts

Fun that this popped back up my feed. Reminds me of a recent Marine Corps commercial/video talking about how retirees are still Marines …… and then they show youngsters who just retired and are in their late 30s/early 40s.

Got me thinking about how folks can look around themselves today not realizing all those old people they see are the prior generations …. Drs, Soldiers, Marines, etc., and how quickly the “middle generations (20s - 40s” become the focus.

I’m closing in on my 7th decade and there are older guys out here as evidenced as the responses. No doubt the question came out of the middle generation.

I’ll just say to the middle generation folks …. You have vets here into their 90s, maybe older, so the line is constantly shifting based on the last/oldest Soldier/Sailor/Airman/Marine whose feet are still above ground!

If you ever;
Wore brown boots,
Carried an M-1,
Ate C rations,
Wore fatigues
Was in a STRAC Unit

If you were issued these, you're old school!!

"Old school" is anyone who was in before you and now brags how hard they had it in their day.

It is in your soul.

You’ve essentially answered your own question by the words “that ever-moving line”. That “line” is determined by the era(s) and branch you served in. In my Army career, that line covered several decades (1972-2001) and “old school” got older every decade. What I thought was “old school” in 1972 was probably thought to be cutting edge stuff to WWII and Korean veterans. So “old school” is however far back your memories can take you. I saw a lot of mine already mentioned in the various comments; some I had forgotten about and others made me realize I AM OLD SCHOOL

Basic I trained with an M14, and cigarettes in the C-rats. Half way thru basic they introduced the M-16, AIT was back to the M-14, got to Vietnam it was the M-16. IN 1973 I took an early out to do a year in the National Guard. Our first weigh in, the crusty old 1st Sgt had each squad load up in a Deuce and a half, and took it to the weigh station and subtracted the weight of the personnel from the truck. We all passed. The 4 mile walk in combat boots the first 24 over the finish line got a beer. 2 years later Did 8 months schooling in Watercraft Engineering Officer course. Came back to a whole new Guard as Top and all the "old guys" were gone. A month later I was pinned WO1. 4 hours later I had a career changing event. I was awarded a full-time dual status Mil-Tech position, but the position called for being enlisted. Some obscure rank inversion regulation, you could not out rank your civilian supervisor in their military position, so they only allowed the supervisors to be officers. I chose to give up the WO. It was wound back to where it didn't exist. Then spent the next 27 years working for the Guard. Retired GS11 and MSgt.