After retiring from teaching maths and computer studies in an 11-to-18 mixed comprehensive, I taught computer studies, part-time, at Channings Wood prison for a few years. Compared with the comprehensive, teaching in the prison was enjoyable, hassle-free and rewarding.
The classes were small, there were no discipline problems (students were in the classes because they wanted to be there) and there was ample equipment. The ability range was probably wider than in the comprehensive but this had its own rewards.
In the same year I had one student who politely corrected a BASIC programme I had written for calculating the great circle distance between two points, and another who was immensely pleased to be able to write and tell his mother that he had gained the only qualification he had ever had (CLAIT).
If I had to go back to teaching, I would choose a prison setting any time. But I would be careful not to find out, even accidentally, why any student was there. It is not relevant to teaching and it could be disturbing.
Newton Abbot, Devon