I read a story somewhere where a mother and daughter swap places (the mother is small and young looking anyway) and go on a road trip by car for several days. Whilst away they buy a school uniform and the mother gets carted off to the school which is very strict. The last part doesn't appeal to me (I'm very much not into spanking/corporal puishment) but the age regression/age progression and role swap does.
I think it was somwhere on the Alt Sex Stories Repository site (http://www.asstr.org/) somewhere but it's a big, extensive site and I've failed to find it so far.
thanks
R