The teachers union accelerated its political spending this month, pouring nearly $1 million into the campaigns of Bill Thompson and other candidates who received the union’s endorsement.

The political committee set up for the United Federation of Teachers, called United for the Future, has so far spent just over $1.5 million on the 2013 elections, campaign filings show. Most has been spent on Thompson, but nearly $300,000 also went to local city council races and $28,000 toward comptroller.

The union is one of several independent groups that have registered with the city’s Campaign Finance Board under new transparency laws that require outside groups to disclose how they’re spending money during the campaign. The expenditures are permitted as long as they are made without input or communication with campaigns.

So far, 14 such groups have filed spending with the campaign finance board, and the teachers union has been the biggest spender. The next highest spender at $1.3 million is Jobs for New York, Inc., a real estate-backed committee that’s focused on local races.

In the mayoral race, the UFT spent $621,000 for three weeks between Aug. 6 and Aug. 30, filings show. That’s a slight increase over the previous three-week filing period total of $580,000.

The spending totals are a monetary symbol of the role that public schools has played in the mayor’s race this summer. Candidates have focused heavily on the education priorities and proposals that they would pursue as the first mayor to inherit control of the school system, although some of those plans have been vague so far.

The UFT endorsed Thompson back in June after months of discussions and internal polling to determine which candidate most matched its interests.

Thompson is the only candidate to pledge to cede control over the Panel for Educational Policy, the body that votes on Department of Education proposals. The panel has never rejected a Bloomberg administration proposal, making it one tool that the UFT and other critics have said the department uses to exclude parents and other community members from the decision-making process.

Thompson has also vowed to end school closures and give teachers $200 a year to spend on classroom supplies.

The union hasn’t picked a winning mayor since David Dinkins in 1989, and President Michael Mulgrew has pledged to steer a significant amount of energy to support Thompson.

“We need to make sure that this entire city school system is about helping teachers help children, and we now have the candidate we know will do that,” Mulgrew said on the day he endorsed Thomson. “And we will fight with him and for him — because he is the next mayor of New York City.”

The Democratic primary election is 11 days away, and Thompson has maintained a relatively steady share of support from Democratic voters in polls. But polls released this week show that Public Advocate Bill de Blasio has extended a lead over Thompson and Speaker Christine Quinn.

The primary would head to an October runoff between the top-two candidates if no one receives 40 percent of the vote on September 10.

The union also began focusing on City Council races in August, spending big in closely-contested races.

The union spent more than $40,000 to support Corey Johnson, who is running for the westside district seat being vacated by Quinn, and $34,000 for Antonio Reynoso, who is running against former state Assemblyman Vito Lopez.

On Aug. 28 alone, the union spent $13,000 alone on mailers for Kirsten Foy, who is running a tight race in Bedford-Stuyvesant and Crown Heights.

More than a dozen council candidates haven’t received any monetary support from the union. Some of the candidates, like Dan Garodnick and Peter Koo, aren’t facing opponents in the Democratic primary. But others are running tighter races, including Micah Kellner, a state Assemblyman who’s being investigated for sexually harassing members of his staff. Some supporters have rescinded support for Kellner amid the allegations, but the endorsement is still listed on the union’s web site.

And in District 41, a race that includes a charter sector-backed candidate that we wrote about on Thursday, the union has not yet spent money to support its candidate, Darlene Mealy.