We have a desk in our hallway that ds1 has started to use for revision. He says there are no distractions.
He went into school today for a two hour revision session which went ok and was promoted in cadets this evening so is a really happy dc today.
Exit, mention that she will need to understand maths a a sahm- cooking needs weights, ratios, percentages, time etc, money has to be managed and budgets written. 
I think that it's more important that they get the grades they need to let them do what they want to do next. Once they are on the next stage the results won't matter much.