Antony Little and Andrew Aalders-Dunthorne will stand for the Conservatives and Liberal Democrats respectively to fight the Labour minister in his Norwich South constituency.
Both teachers claim they are confident of beating Mr Clarke and say they will have better credibility on education issues because of their classroom experience.
Mr Little, the Tory candidate, teaches history at Notre Dame secondary school in Norwich. He taught Mr Clarke's son Christopher while on teaching practice, but insists he will not be using this experience as blackmail.
Mr Little, 25, said other teachers had been supportive but that his students had laughed when they discovered how young he was.
"My pupils did not know my first name or my age until they saw them in the local press," he said. "One of them told me that voters might confuse me with Charles Clarke. I am a bit on the rotund side, but I've not got the beard."
For Mr Aalders-Dunthorne, who teaches at Bignold middle school in Norwich, it will be the third time he has stood for the Liberal Democrats against Mr Clarke.
Mr Aalders-Dunthorne often brings his own political experiences into lessons on citizenship and is getting a class to decide where they should go on an outing by using proportional representation.
"The children can see that if 14 boys vote for football, they would win under the first past the post system," he said.
"But if we use the single transferable vote system they might choose something which both the boys and girls would enjoy."
Mr Clarke won the last election with a majority of 8,816 over a Conservative candidate.