From my own knowledge, there will be a prison officer in the 'classroom' to watch and monitor. I don't remember if there were others in the classroom but there will be others very nearby.
There will be an alarm bell button in the room and my advice would be to position your main working area within arms reach. Unless it's next to the officer's desk in which case they will hit it fast if it is needed.
You will get prisoners who are there because they have been told they have to be and others who are there because they want to be.
The prisoners will all be on an incentives and earned privileges scheme where poor behaviour can be reported.
You will be required to write reports about the prisoners and their engagement in education, or lack of, for offender management reports. This goes towards their progress through the prison system and can be used in parole reports.
You will need to undertake training in personal protection, provided by the prison service, this may include hostage negotiation as anyone could end up involved. It's not to scare you but to prepare you. You will not be trained to the same level as prison officers but given enough knowledge to know how to breakaway and to have some knowledge of how the protective systems work, e.g. Control and Restraint, negotiation, conditioning - when a prisoner gets you into a position (through essentially flattery) where you might be asked to break the rules, and you actually consider or do it.
Much of the time as pp says, you will be dealing with people with lower academic levels than general public. Many prisoners have been repeatedly failed in life from early childhood and therefore not engaged effectively in education. There is a higher percentage of adults with diagnosed behaviour disorders and mental health conditions in the prison population so before you even consider that they may have committed an offence they are also dealing with that.
However; teaching adults and getting them engaged in their learning is as important and rewarding as it is for children when it goes well.