A so-called extra measure of punishment flaunted by commonly blinded insensitive burnt-out figures held in educative authority. This punishment requires the offending student to go out of their way in the free time they have at the start of their weekend and spend two or so hours at their school doing what the attending teacher requires them to do.
From my school, this is the result of getting two detentions in a week or getting a very low negative behaviour point score by the end of the school week.
It is a wide-held belief that detention is to make the student reflect on their bad behaviour and hopefully have them avoid this punishment in the future. From what I've seen, this kind of detention not only deviates from that desired effect but also worsens the effect that teachers wanted to avoid in the first place.
I've seen some of my friends and many classmates getting this type of detention and it didn't help with their behaviour in the slightest - it only made them get even more detentions, resulting in them returning to even more Saturday detentions.
If a student has done so bad to constantly be given Saturday detentions, chances are there is an underlying issue with said student that needs to be addressed, worked, and resolved, as opposed to just doling out detentions like government cheese.
Teacher: Jimmy, that's two lates in a week. You have a Saturday detention starting at 11 am.
Jimmy: Whatever.
Teacher: And another one now for the following weekend.