These are often people who have had a very bad start in life, who may have been deprived of a secure family and home (care leavers are significantly over-represented in the prison population), and who often have very few literacy and numeracy skills. On top of that, 10% of men and 30% of women prisoners have received inpatient psychiatric treatment, and many others have mental health issues.
Whilst I think it's a good idea that prisoners actually do something useful for part of the day, and this may include physical work, I also believe they should be housed in decent prisons, given access to fresh air and exercise and given a chance to catch up educationally. I don't think that should just be learning reading, writing and arithmetic, but also the opportunity to enjoy the arts - painting, singing, drama - all of which are known to be beneficial in improving self esteem and creating a more confident and positive approach to life.
Some of the people on a course I attended worked as literacy teachers in prisons and they said the commonly held view that prisoners had a "cushy life" would soon be dispelled if the people confidently putting forward such an opinion actually visited a prison and saw the tragedy of it.
I think the state of our prisons, in a country as rich as ours, is a national disgrace.