Most of my teachers at my Grammar school were ex forces. Hard but fair.
Fuck with them and they would fuck with you.
Play fair, it came back in spades - they were all dying to impart their wisdom (including how to strip a BMC A-series engine) to those that chose to learn.
The vast majority got the point - even those that we thought would be kicked out - and a few did at O level stage. They went on to be successful in life, if not in school. BUT they learned the value of learning and the need to constantly educate youself - in what any way suits you.
The hunger for knowledge should always outweigh the hunger for food. No-one in this country will ever starve.
I left school with only eight O levels and two A levels (piss poor for that school) but it taught me discipline and the want to constantly learn.
For that, I have ex Army, RAF and Navy teachers to thank.
Even Mr Scoble and his "loose" Physics lessons where he went on about his apiary, how wasps were cunning bastards, and what pipe he was going to buy next, were educational.
He held a class in awe. He was about sixty five then and still held two of the P.E. Classes each week. He taught
and still flattened all the sixth formers.
Hard man. Hard rules. We all loved him. He even re-valved my smoking Austin 1300 as part of a project when I was seventeen.