When I worked for the Texas prisons, the inmates weren't "required" to work, but if they didn't, their privileges were substantially reduced. E.g. no commisary, no time in the rec yard, no visitation except for their lawyer.
Then again, when I worked for them, they were being watched for civil rights violations as a result of losing a class action suit. I had it on good authority that when the oversight was gone, it would be back to the good old days of gratuitous brutality.