Here in NM, there are 6 prisons. I am only familiar with the main penitentiary, as I worked there for a little while. But the way things work is:
There are 3 sections the prison is broken down into. Level II, Level V, and Level VI.
Level II is for your minimum security risk inmates. Those who will be getting out soon, those who have very little time, or those that pose no actual risk. Mainly general population inmates are housed here. They go to chow, just like you would at school, one dorm house at a time, and are allowed commissary, unless of course they get in trouble or something along those lines. But it's pretty lax.
Level V is for those who can't function in general pop. Those that aren't necessarily lifers, although some could be, but they do have quite a few years on their record, or are repeat offenders. Generally, these prisoners have a rec area that they can gather at, but are housed in individual cells, some have cellies, or cell mates because of over crowding, but they have the ability to get help. They take classes, they have access to a library, but it is strict in regards to what they can and can't check out, depending on the circumstances, books can be requested and taken to their cells if they are not allowed the time to go themselves. They have rec time outside for a certain amount of hours per week. Etc. Visitation is allowed, but it is by appointment only from an approved list of visitors. Depending on the circumstances, the visitation can be a contact visitation, but it has to be approved by the warden.
Level VI is for your murderers, lifers and mentally unstable prisoners. Those who can't function around others at all. They are housed in their own cells, 23 hours of the day. With 1 hour for rec, which is done in another cell outside. In other words, they are transported by an officer from their cell, to the caged in area outside that is specified for them to walk around, exercise, or whatever. They are cuffed, then taken to the cage, where they are locked in and then un-cuffed through a grate, to minimize the possible danger they are to the corrections officers or themselves. These inmates, while given the opportunity to read or correspond, are limited. They have hours for visitation, but it is by appointment only and is limited to immediate family only. They have to be approved on the list of visitors as well. They can only talk to each other via telephone and can see each other through bullet proof plexi glass. there is no contact with the visitors. Religious or academic services are done in a room, where each inmate is housed in their own cell, and an instructor or pastor is outside in the hall way. Again, no contact.
The thing is, those in Level VI will probably never see the light of day outside those walls. So they don't bother really to rehabilitate or educate them for the possible outside world because they will never be a chance for that.
Also, meals are delivered from Level II to Levels V and VI, and are delivered to each cell, by 3 officers. One to open the food grate, one to stand by with a shield in case the inmate tries anything, and the other to slide the tray in.
If an inmate does something that an officer deems inappropriate or causes trouble, the food rations for that day are delivered in what is called a food loaf. Basically, it's all the nutrients you would get for the days meals, but in a very unappetizing, meatloaf type thing...I've had to make those, I know what they are, and it's disgusting.
Bagged lunches are given for lunch, sandwich meat, bread, a piece of fruit and a carton of milk.
All utensils or food trays are very limited and are made in such a way so when they go to the maximum areas, the inmates do not have anything that can be later made into a weapon.
I hope I didn't confuse anyone...It's been a while since I worked there so I'm trying to remember everything off hand.