Pondering this today. The ideas I have come up with so far.
- The children are so knackered by Friday afternoon that there is no point trying to teach them (not a dig, DS is actually very tired)
- So they have a punishment (ie you have lost 5 mins of your golden time), but actually this is probably a useful byproduct of the real reason.
- Teacher gets to observe social interaction - actually this is maybe the official reason.
Any teachers out there who can tell me the real reason.