When I went to school some 30 years ago after school detentions were seen as nothing really. These days they tend to involve SLT's taking them, letters home follow ups about the Pupils conduct and it requires a pupil to generally have misbehaved quite badly to get one.
The difference in approach or meaning of after school detention, can be compared with my 20 or so through my secondary schooling and DD1s who is in year 11 1. DD 1 was distraught when she got a after school detention in year 10 whereas my year group used to laugh and actively seek to be the first one to acquire one. It sounds silly but an a after school detention was seen as a badge of honour with the highest value going to the girl with the most. This was by the way a Girls Grammar in the late 1980s early 1990s, so not really difference from DDs1 current school inn character.
However, DD2 year 9 goes to a non grammar school where there does appear to be a group of girls who get regular detentions . These girls have dragged DD2 in to detention on three occasions because she thinks its cool to engage with their stupidity at times.
Therefore, are detentions today seen more of a serious sanction today, than when they were given out by bored teachers who had to stay late. This was said to me and four friends one day in Physics!