ALBANY — New legislation would bar New York’s charter schools from expanding their grade offerings as a budget fight between Gov. Kathy Hochul and the state Legislature heats up over the issue.

Just 460 charters are allowed statewide, but they can add new grade levels as students grow older — a so-called loophole their opponents want to close.

“There’s a whole multitude of problems that exist with arbitrarily letting a charter expand their horizons, and where does it stop?” Assembly Education Committee Chair Michael Benedetto (D-Bronx) said about the bill he sponsored in his chamber.

State Senate Education Committee Chair Shelley Mayer (D-Yonkers) introduced the legislation, which has made no progress in two prior sessions, into her chamber earlier this year.

Both Benedetto and Mayer are known for opposing changes to current charter school grade limits with the support of organized labor.

The timing of the bill’s introduction in the Assembly is notable since Hochul and legislative leaders remain locked in budget talks 20 days past an April 1 deadline — with the governor holding out for concessions on issues like charters.

The matter is expected to come to a head soon now that Albany Democrats have reportedly struck deals on loosening cash bail limits while giving up on including any sort of comprehensive housing plan in a final spending bill.

“Hochul is right to stick to her guns,” Success Academy Charter Schools CEO Eva Moskowitz told The Post on Thursday.

“There is no virtue in passing a bad budget quickly.”

Approximately 100 more charters could open in New York City if Hochul can convince Assembly Speaker Carl Heastie (D-Bronx) and state Senate Majority Leader Andrea Stewart-Cousins (D-Yonkers) to go along.

The first proposal would eliminate the 275-charter limit within the five boroughs while the second proposal would allow so-called “zombie” charter school licenses to be reissued — ideas many Democratic legislators fervently oppose with the support of teachers’ unions who have showered many of them with campaign cash.

Union allies said Thursday they were not budging — no matter the pressure from Hochul.

“There’s no room for wiggly because there is no wiggliness necessary,” state Senate New York City Education Chair John Liu (D-Queens) said when asked if he had any “wiggle room” on allowing more charters.

An official from New York State United Teachers — whose biggest subsidiary is NYC’s United Federation of Teachers — was seen walking through the Capitol and Legislative Office Building in Albany to press lawmakers from both parties to publicly state their opposition to charter expansion.

“We’ll continue to stand strong against the expansion of charter schools,” Assemblyman Steve Stern (D-Huntington) told NYSUT legislative rep Jim Larson, who brought a packet of letters to Stern’s Albany office from teachers in his district.

“We’re going to make sure we stand strong for our public schools,” Assemblywoman Kimberly Jean-Pierre (D-Lindenhurst) similarly told Larson.

The intensity of the renewed anti-charter offensive has made an impression on some legislators.

“If I were to compare the lobbying that we’re seeing from the two sides, NYSUT really does seem to be running circles around them,” Assemblyman Jarett Gandolfo (R-Bayport) told The Post after pledging his own opposition to expanding charters at the behest of Larson.

But supporters are holding out hope that Hochul might somehow secure at least some charter gains for the Big Apple.

“I hope there is a possibility of zombies coming into the budget and moving some of the regular charters numbers in New York City,” Assemblyman Brian Cunningham (D-Brooklyn) said.

“I hope there is a possibility of that but nothing is confirmed.”

Hochul also could exercise her gubernatorial powers to their limit in the charter fight now that budget talks on bail and affordable housing have largely ended with mixed results for the governor.

“I don’t actually think there have been meaningful three-way discussions on this,” said state Sen. Kevin Thomas (D-Garden City), a charter supporter.

“It might be time to move to education.”

Benedetto notably declined to say whether he would want a limit on expanding grades in a potential budget deal that might allow more charters to open.

“I never want to comment on ongoing negotiations that are going on with the Assembly and the Senate and the [governor],” he said.

Benedetto added that he waited until the middle of a budget fight to introduce his bill into the political conversation because he “frankly just forgot.”

A Hochul spokeswoman did not immediately respond to a request for comment.