A school visited by a boy with leukemia will conduct tests with stem cell donations to find a match.
The parents of five-year-old Oscar Saxelby-Lee from Worcester said they needed the "friendliness of a stranger" to save their child's life.
He needed a transplant within three months of his chemotherapy, or his chances of survival would "decrease significantly," his family said.
They also call on the public to register with the NHS blood stem cell registry.
Mother Olivia Saxelby (23) and father Jamie Lee (26) initially thought Oscar was anemic after feeling unwell over Christmas.
After a blood test, however, the diagnosis of acute lymphoblastic leukemia was made.
He has had 20 blood transfusions, four weeks of chemotherapy, and is being treated by doctors at Birmingham Children's Hospital.
You may also be interested
Worcester's Pitmaston Primary School is hosting a blood stem cell registration event next month.
- Latest news and updates from the West Midlands
Schoolteacher Kate Wilcock said: "I was shocked that such an open-minded, happy, little, naughty guy was hit by such a serious illness.
"The kids were amazing with their reaction, openness, generosity and love for Oscar."
Ms. Wilcock said she "could not stress enough how important it is for people to come down and register."
The tests will expire on March 2 and 3 from 9:00 to 15:00 GMT.
Ms. Saxelby and Mr. Lee are not strong enough stem cell fights for Oscar.
"The donor does not have to be a relative and could come from the friendliness of a stranger," said Ms. Saxelby.
If no match can be found, Mr. Lee's cells are used, but his family said there were certain "risks" involved.
"It's five minutes for a smear, but you could save someone's life," added Ms. Saxelby.
Follow the BBC West Midlands up Facebook, on Twitter, and Sign up for local news directly on your phone,