My latest find for a 1 gB Ram 1 CPU VPS works out at 79 cents a month for full access. Only had to put $2 down to be away. Plus I still have a free 12 month VPS from another supplier. Not sure if I would trust my under $1 a month with a classroom of students and all their work but I ran over 700 students in total and with over 50 logged on at once on a $5 a month VPS.
I think current VPS prices, always on internet access, and ease of setup make the home computer sandbox setup redundant,