Keeping kids at home from school when they get sick is one of the most important ways to stop the spread of swine flu.

But plenty of parents can’t skip a day of work to watch their children – and that worries the hero school nurse who first detected the virus in New York.

The head nurse at St. Francis Preparatory – the Queens school that became the epicenter of swine flu in the spring – says New York City needs a law to force all employers to provide paid sick days.

"At a school where the parents have no sick days or are afraid they’ll lose their jobs, swine flu will be a whole different disaster," Mary Pappas said.

Studies show that as many as 1 million city workers – some 39% of public school parents – don’t have any paid sick days, including most of those in food service and a majority of low-wage workers.

Pappas today will join leaders pushing for the bill at a demonstration in front of the Department of Education, where she’ll urge Mayor Bloomberg and the City Council to act fast.

"St. Francis Prep was able to have a fluid process because the parents were able to leave their jobs if their kids were sick," said Pappas, who saw 1,000 teens exposed to the virus after a group of students returned from a trip to Mexico, closing the school for 11 days.

"If I was in a school where there’s a different economic status, where parents have no sick days, I don’t know what kind of chaos I would have had," she said.

City Councilwoman Gale Brewer (D-Manhattan) introduced a bill** last month that would give all private-sector workers in New York City access to paid sick days. It already has the support of 36 Council members and the Working Families Party, which has lobbied hard for the legislation.

The new law would force businesses with more than 10 employees to give workers nine annual paid sick days. Employees at smaller businesses would get five annual sick days.

Bloomberg said last week that one of the essentials to curtail the spread of swine flu is to isolate the sick.

"These parents are up against a wall," Pappas said. "The bill would really help."

"The mayor is talking about swine flu and says what you have to do is keep your kids home if they have symptoms," she said. "If you’re a parent without sick days, you can’t do that."

** With support from Make the Road New York