Prison education staff at the institutions run by the Manchester College, which is the largest single provider of prison education in the UK, walked out on Wednesday over plans to reduce holiday and sickness entitlement while increasing hours.
The University and College Union (UCU) said that some staff would also be forced to move to new pay scales which would see them lose up to pound;7,000 a year.
Alan Whitaker, UCU president, who will be speaking at the rally in Manchester, said: "Our members don't want to take strike action, but they have been left with no choice. It is deeply concerning that Britain's largest prison education provider is trying to force through new contracts that will seriously jeopardise prison education in this country.
"The new contracts would mean fewer rehabilitation opportunities for offenders. UCU believes education must be at the heart of any reform of our prison system and the evidence backs us up."
UCU members held a rally on Wednesday at the Manchester Conference Centre Institute, where Mr Whitaker and prison teachers addressed the strikers.
The union said prison education is the key factor in cutting reoffending, saying that over half of all crime committed in the country is by people who have been through the prison system and that studies show prisoners who do not take part in education are three times more likely to be reconvicted than those that do.
UCU said 78 per cent of members voted to strike, with a turnout of 51 per cent.
A spokeswoman for the college said: "The strike is regarding a dispute over necessary changes to contracts to ensure the long-term viability of an effective and efficient learner-focused service. More than 80 per cent of staff have already signed their new contract."