I did mention solvents (googling can lead you into wicked ways
)
I think linspins meant this bit though:
'Soak in room temperature water for 24 hours if the glue has already dried. It needs to soak for many hours in order to soften the glue enough that it can be scraped off. Try using a stiff cleaning brush to remove the glue from the cloth fibers, and then wash with laundry detergent. This may need to be repeated to remove all of the glue.'
which fits with soaking the brushes at school.
sunchild, it might be a good idea to soak a clean teatowel (or similar) & lay it on top of the dried glue to give it a chance to really wet the glue.
Or nip at it with fine scissors.
(Or get a new carpet
)