What constitutes being "old school" in the military?

Old school would be whenever you served as compared to today. As such the definitition is somewhat malleable.

back again : all except mres . but i dont consider myself old school, i am just old, it has been 40 yrs since ets . thanks all for the memories .

My DI defined "Old school" as anyone that entered the service a day before you entered..

Everything from Vietnam to Desert Storm and all the games in between steel pots to kevlar you name it and I was somewhere near it.

Wore white tee’s, barrack’s chore in winter, keeping the WWII barrack’s furnace stoked at night, on K- P scraping down the company’s coal fired range, cleaning the kitchen’s grease pit, post beer bars, pass bus.

Any comment of "I'm old school" should be followed with the question of how many years have you been in. Claiming to be old school and being old school are two different things. I would never claim to be old school, but it someone were to say I was old school, I might take that as a complement. Context is everything.
No, I would not mind having that reputation, for most things.

I got my license on an M151A1 jeep and was assigned a willy's 3/4ton with a Rat-Rig on the back with a VRC46 & 47 and a Vincent aboard.

If you think all the younger people are weak, lazy, undisciplined, and have it too easy... There will always be a group of lazier or less motivated junior enlisted, but that's partly our job as leaders to mold as many as we can into our image of what a military professional ought to be. When we call ourselves old school I think what that really means is that we are inadvertently acknowledging that we are becoming over the hill.

You are old school army if you:
Sang filthy Jodies on a battalion run
Did PT exclusively in combat boots
Smoked and spit tobacco in the TOC and during office meetings
Saw exotic dancers during Happy Hour at the I-Bar at Fort Benning's O'Club
Actually had an O'Club and an NCO Club on post
Remember the first day you had to wear BDU's to formation to prove you owned a set
Mess Sergeants who actually cooked in the field
Couldn't ask and you couldn't tell
Your primary helicopters were a UH-1H, OH-58C, and the AH-1S
NVGs covered your whole face and you only had a grainy 40 degree field of view
Remember the AN-PRC-77 you had on your back hitting you in the back of your head as you fell over a log during a patrol in the woods (TMI?)

hihi Been there done that.