An online petition that a Brooklyn teacher created in a moment of frustration this spring is bringing renewed attention to the fact that city educators do not get any paid family leave.

In the last day, more than 25,000 people have signed a Change.org petition calling on Michael Mulgrew, the city teachers union president, to fight for paid leave for his union’s members.

The petition’s creator, Emily James, is like many city teachers who have had children: Having spent more sick days than she has, she allocates $300 a month to “buy back” time she owes the school system and comes to school sick because she can’t afford to take more days off.

It’s a situation that many teachers wind up in because, rather than receiving any paid leave, union members must use their own accrued sick days to take time off after having a child.

When Mayor Bill de Blasio announced that city employees who have children would get six weeks of paid leave, it seemed possible that the policy could change. But de Blasio’s policy does not does not apply to city workers who are members of unions, which must negotiate leave policies into their contracts with the city.

“How hard could it be?” asked James. “It just seems like, of all the things they fight for and negotiate for tooth and nail — and they seem pretty powerful — it seems like if they wanted to negotiate this for us they could do it.”

James said she first created the petition with a friend in May after hearing that Mulgrew had won a big promise from de Blasio: free parking for city teachers.

“We just looked at each other and thought, ‘This is what they’re negotiating for?’” James recalled.

In fact, the city and United Federation of Teachers have discussed the prospect of extending the city policy to teachers. But those discussions “have been fruitless so far,” according to a union spokesman, Dick Riley.

A City Hall spokeswoman suggested the UFT members could potentially look forward to a changed policy — in a year or more.

“We had initial discussions with the UFT and we look forward to continuing our discussions, as we will with any union interested,” said the spokeswoman, Freddi Goldstein. “It’s a benefit that must be dealt with during contract negotiations and we’ll be having those conversations during the next round of collective bargaining.”

The UFT’s current contract runs through October 2018, so contract talks could start soon. But the expiration date is no guarantee of a new contract: The union’s current contract was ratified nearly five years after the previous contract expired.

Meanwhile, James’s petition received another 4,000 signatures overnight, along with a slew of comments from teachers who describe the stress and financial burden of having children while teaching in city schools.

Some of the teachers say they are making significant decisions based on the current policy.

“I am a NYC teacher and want to start my own family within the near future,” one wrote. “I have been delaying it because I want to save up more days.”