I think the real problem is that the people in jail are largely irredeemable. Most were raised as feral children with no adult supervision or real love. By the time you "raise" a child without love, they are broken by age 6 or earlier. Then a lot of them are heavily genetically disposed to alcoholism and drug addiction. Then a lot of them are dumber than mud. To make it in a trade, you need to be literate, be able to work independently and have some pretty good basic math skills and be able to have plans beyond getting phucked up. The people that worked on our home remodel were clean, hard working, honest, smart, competent and well paid.
I suppose you could run a strong triage program to pre-select only strong candidates for your trade program, but the left wouldn't like the selectees. They wouldn't like the demographics and the requirement that they know how to read and do basic math. Like all government programs, the point of the program isn't to get people to succeed to the best of their ability, it's to pretend that everyone can be a doctor or an astronaut.
The trade program would be great, if it started in middle school, with reading and basic math used to plan for material requirements, the ability to follow written directions and then the ability to do plumbing, electrical wiring, tile work and cabinetry and detailed woodwork, like door and window framing. Even painting requires math and the ability to do quality fine work. Our Costa Rican counter top guys are using computerized cutting for their quartz countertops and the Russian cabinet guy is also using computerized wood saws.
One of our old neighbors was an electrical engineer for one of the Portland chip makers. He was smart and yet dumber than a bag of hammers and literally one of the ugliest men I have ever seen. He was his wife's second husband. She once would have been moderately attractive but the extra 50 pounds and a tough life left her with the choice of getting married to a paycheck and then hanging at home and smoking cigarettes and drinking chardonnay or else? She had a 20 year old son from her previous marriage who got his girlfriend pregnant and had twins. He hardly ever saw them. No way he could pay child support unless his step dad did it. He didn't work and just hung out at their house and did absolutely nothing. So, Safeway went on strike and they were hiring anything that moved to replace the strikers. He got a job stocking groceries. He had a party at their house after day one to celebrate. Called in sick for day two and got fired. I think to "redeem" that kid, would have taken a whip and constant supervision. The likelihood of him turning into a self-starter would have been nil.
I heard a riveting interview on the PBD Podcast of Roger Reeves, who was a pilot smuggler for Escobar. His idea for prison reform is that we turn the prisons into a type of trade school. Not for lifers, but for those serving 5-10-15 years. The idea is that they get sent in to serve 10 years, but study a trade like plumbing, welding, carpentry, etc. Then upon release, they have a valuable skill with which to build a new life. I have a feeling the way the prison system is set up now it is probably making certain people tons of money just like the pharmaceutical industry. Nevertheless, I think it's an idea that should be seriously explored.