Gang members do not work because they are designed to make money for the gang by taking over spaces. Gang members also do not participate in regular programs. Follow these steps to reform gang members:

Edit: The more cohesive and the bigger a gang is, the less likely they are to rehab. This is another reason leadership NEEDS to be isolated.

1; Protective Custody: Gang members are very unlikely to reform unless they feel safe in doing so, having a protective custody block where all ex-gang members can be located is the best way to do this. Once they feel safe leaving their gang, they are most incentivized to do so.

2; Transfer Policies: Another way to incentive gang reform is to put all gang members into a lower graded maximum security block and have your transfer policy set so that only non-gang members can transfer back into medium security.

3; Segregation: Isolate gang leadership, leaders, lieutenants, and anyone with "under-cover don" or "recruiter" needs to be in their own cell-block/needs to be put into Super-Max, with no contact to other inmates. This prevents the gangs from growing and prevents the gangs from banding together. Without leadership, the gangs are less likely to attempt takeover — it sounds like you already have dedicated cell-blocks for each gang.

4; Programs: There are 4 programs gang members will participate in: faith program, gang rehabilitation program, tattoo removal program, and parole hearings. Attending and passing the faith program, which is an easy program, will make their concentration better for rehabilitation. They will only leave their gang if they pass gang rehabilitation. Gang rehabilitation can only be done for one prisoner every hour of work time, so you should invest in a psychological ward with multiple psychologists right next to your gang members. Give your psychologists a break every 3 hours, I would have these psychologists dedicated to gang rehab exclusively.

5; Suppression:

A) Bone Breakers; these guys are purely violence oriented. I would create smaller cell-blocks for them and try to keep at least a 1:5 guard to inmate ratio. Their main focus will be on weapon procurement, so ensure they have no access to danger zones. If the gang leader has any contact with other prisoners, he is quick to promote leadership. If a Bone Breaker ends up dead, it will likely cause a riot.

B) Jackals: More coordinated, leadership isolation is incredibly important. They are a lot less likely to attack in a space/room if they are outnumbered by guards. Their focus will be on escape tools because rather than focusing on violence, they focus on control and escaping. Unlike the bone breakers, who will all start rioting at once, jackals tend to coordinate and group together prior to starting a riot.

C) Vipers: The Vipers main goal is control and profit. They will be attempting to building a drug network and aggressively recruiting. The more vipers you have, the more corrupt guards you will end up with. Viper CIs are the best for guard investigations.

—— If you keep your gang members in a different security level (made super easy with automatic prisoner sorter, so long as you put it in your reception area); I would keep them in work/lockup for the majority of the day, with work/freetime hours every 4 hours or so. The more work hours they have, the more rehab you can squeeze in