Randy Ramadhar Singh from Tolworth girls' in Surbiton, Surrey, ate two teaspoonfuls of Felix cat food in front of around 400 pupils and teachers to raise money for hurricane victims in the Caribbean.
The Trinidad-born physics teacher said the cat food tasted disgusting but he carried out the stunt to show how desperate starving islanders would be.
He said: "We had been covering world hunger in my Year 8 tutor group when the hurricane struck Grenada this autumn. Being from a small island, I knew what the destruction would be like and discussed what lengths starving people would go to.
"Pupils asked if I would eat cat food if starving, and I said I probably would.
"They then offered to raise money to see me eat cat food and when it became obvious they were serious I felt I could not back down."
Mr Ramadhar Singh, 29, who has worked at the school for more than two years, said he could not recommend the experience.
He said: "It tasted awful. I had to run off and rinse my mouth out afterwards. But seeing how keen the pupils were to raise money for such a good cause was worth the humiliation."
A Food Standards Agency spokesman said: "It sounds odd, but meat destined for pet food still has to be fit for human consumption."
A spokeswoman for the Department of Health said: "It is his personal choice if he wants to eat cat food, but cat food is obviously for cats, not humans."
Mr Ramadhar Singh raised around pound;200 after pupils and staff paid 50p each to watch the performance last month. The 1,300-pupil school for 11 to 19-year-olds has raised more than pound;2,000 for islanders.
Emergency supplies such as soap and milk powder, donated by pupils and parents, have already been shipped out to the Caribbean.