This made a noticeable difference...
http://en.wikipedia.org/wiki/Children_Act_1989 It was implemented in October 1991 iirc at my school. And the effect was instantaneous

Upto that point the school had a strictly enforced punishment system which generally benefited the school community as a whole, but were individually inconvenient enough to bugger your day up...
You had to report to the duty staff in PE kit at 07:30, morning break, 13:30, Low tea ( about 15 minutes after last lesson) and High Tea. After 18:45 you were then confined to your house except for official activities such as swimming. Had to remain in uniform all day, normally you would change after last lesson. You were reasonably expected to do litter picking on or around the school grounds, or a run or standing as an example, depending on what the member of staff saw fit.
1. Minor misdemeanors resulted in a Task Card. Report as above for twentyfour hours from issue. Card had to be signed each time.
2. Daily Detention, as 1. but included an hours supervision between Low Tea and High Tea.
3. Slightly more serious items would result in a Detention, report at meal times in uniform, and spend two hours under supervision on a Saturday evening after High Tea, when everyone else was either watching videos or having discos.
4. House Gating, for significant transgressions such as smoking/drinking, resulted in 1. and 3. plus being confined to the house outside of lessons, and being required to wear your uniform at all times.
After October 1991, the reporting element was reduced to simply reporting, and only requiring uniform tobe worn for the afterschool items if you were 'gated' as litter picking et al were suddenly deemed to be demeaning. It's a punishment ffs, it's not supposed to be nice

As for the unofficial punishment system, that was a hierarchy. If you crossed an unwritten line, then the error of your ways was generally beaten into you, repeatedly until the point was made. Sure some House Prefects got off on that and went a bit far, but more often than not, the recipient had actively sought the outcome that they received... keep poking a bear it will bite. By the time I reached the Sixth Form, there were a hard core of shits who had no respect for there peers, the staff, the community as a whole, and certainly not for their elders.
All you would hear from them was 'You can't do that, the Child Act says so... so what are you going to to about it'
Found that a 3am raid was always effective, every day for a week. Their peers soon got fed up with being woken by their beds being upended every night. Sneaking into their dorms for a crafty smoke always used to leave alot of explaining for them in the morning too

If the effects of the Child Act were apparent to a 15-18 year old here...
http://www.kesw.org/ I can't begin to imagine what the local comprehensive was like