I had a folding table for my DD when she was a teenager. It outlasted her school days. I got a cheap one from Ikea. It was very sturdy and excellent value. It was mounted on to a solid wall. DD was delighted with it and started assembling it as soon as we got home. DH finished it before bed.
From memory, it was folded flat against the wall very infrequently - but, the knowledge it could be folded flat was very important. The table had a sort of shelf return so that there was still space for some items on the table when folded flat, and we had an enormous shelf unit above so that there was plenty of "tidying up" places.
Daughter enjoyed folding away her study table (and homework) in the holidays and when she had friends over.
As a student I had a study bedroom with a length of kitchen worktop along one wall - I loved having a really big surface to work on and keep things handy and the depth was perfect. There was practically no-where to lounge though, except the bed. I never minded.
I guess it's a personal decision and I'd suggest asking your girls for their views.