Baby sitter wanted. Lightsaber experience, basketball skills and willingness to wrestle are a plus.

With more families entrusting young children to the care of male baby sitters, teenage boys—many who couldn't care less about old notions of gender roles—are discovering an enjoyable alternative to mowing lawns for extra cash.

The American Red Cross says it has noticed an uptick in the number of boys taking its baby-sitting classes, which are held in more than 2,000 U.S. classrooms. This year, 9.3% of its enrolled students are boys, up from 8.7% in the year ended June 2013. The number could approach 11% after the summer busy season, the organization says.

Grant Hansen, director of product development at the American Red Cross, says the organization decided to feature male sitters in instructional materials in its Advanced Child Care Training course for ages 16 and up, launched in April, after hearing from instructors that there were more boys taking classes.

Baby sitting is a good job for either boys or girls, Mr. Hansen says. "There's a difference between good baby sitters and bad baby sitters, and I don't think gender plays a role."