The five- to 11-year-old children at Broad Oak Primary School in Manchester have been shown a DVD telling them the right and wrong ways to act when they have a cold.
But one parent condemned the exercise as "a complete waste of time".
The parent added: "I send my kids to school to learn, not for someone to show them how to blow their nose.
"My lad said 'Everyone knows how to blow their nose, we know to use a hanky not our sleeve'."
Pupils have also been asked to look at a Kleenex-sponsored website at home with their parents, called Sneezesafe, to help them understand cold germs and how they are spread.
Aimed at four- to six-year-olds, it tells the story of two schoolchildren characters who get colds, and how they try to stop them being spread.
Under the heading 'Tissues to the rescue!', children are told: "Nathan still has a runny nose, but now he knows that sniffing is not very nice. And Nathan is not going to wipe his nose on his sleeve. He's going to blow his nose with a tissue.
"He holds the tissue to his nose, breathes in, then closes his mouth and blows his nose.
"Good boy, Nathan! You've blown your nose properly. The germs are in the tissue, not in the air or on your hands."
Sheila Marchant, headmistress at the primary school, said she believed the school was being responsible in trying to reduce the spread of colds.
She said: "It is in the curriculum to teach children safe hygiene from an early age. And at this time of year, there are many cold and flu bugs around." (By Stephen Adams Last Updated: 9:04AM GMT 30 Dec 2008)