The new class-size reduction law for New York City has too many loopholes to make the huge impact some predicted any time soon, concerned educators and advocates told The Post.

The law, which limits the number of students in classes from kindergarten to 12th grade, has four major exemptions that the Department of Education can use to sidestep the mandates, sources said.

The exemptions cover: lack of space, “over-enrolled” programs, a shortage of licensed teachers, and schools in “severe economic distress.”

Space and staffing pose the biggest hurdles.

Currently, the DOE cites licensed teacher shortages in middle- and high-school English, math, the sciences, and Spanish, as well as bilingual and special-ed.

And the UFT can negotiate higher class sizes for elective and specialty classes if the majority of staff in a school agree.

“This law will barely impact high schools and most middle schools,” a math teacher predicted. “It’s the quintessential bait and switch.”

Chancellor David Banks has appointed a 48-member Class Size Working Group — including parents, teachers, administrators, and education advocates — to come up with recommendations by October on how the DOE should carry out the law.

In a first meeting this month, the law’s loopholes were barely mentioned.

“One of my concerns is that these exemptions are going to be heavily used and heavily relied on to circumvent the implementation,” said member Ron Britt, a Queen’s dad of four and education chairman of the NAACP’s Jamaica branch.

The law, signed by Gov. Hochul last September, caps kindergarten through third-grade classes at 20 students, fourth through eighth grade at 23, and high school at 25.

DOE officials posted data this week showing that 61% of K-12 classes — including only English, math, science, and social studies in high school — currently exceed the new caps, and 39% are already in compliance.

Under the law, the city must have 20% of classes meet the caps by 2023-24, and 40% by 2024-25.

“We are on track to be in compliance for years 1 and 2,” according to the DOE.

But compliance must increase to 60% in the third year, 80% in the fourth year, and 100% by 2027-28.

That will require a massive effort to recruit a projected 7,000 new teachers at an estimated cost of $1 billion a year. 

“If you’re going to phase this in over time, you need to start now,” Britt said, adding that he hasn’t seen a sense of urgency by Banks or other DOE leaders.

The licensed teacher shortages should raise a red flag, said Leonie Haimson, executive director of Class Size Matters and a group member.

“The NYC  teaching force has shrunk by 4,000 positions over the last five years, and will further shrink if the Mayor’s budget cuts are adopted.

“It emphasizes the need for DOE to start hiring more teachers now, and not coast for the first two years, which is what they’re currently doing,” Haimson said. “It’s as if by dragging their feet, they are preparing to say when year three comes around, ‘We just can’t do it.’” 

Instead of boosting new construction, the city is cutting $2.3 billion from the DOE’s capital plan, a reduction of 21,000 seats –” just when we need more seats” to cut class sizes, Haimson said.

But the DOE can’t simply cite an exemption as an excuse not to comply. 

Under the law, all exemptions must be approved by both the teachers’ union and the principals’ union.

If the three entities can’t agree, an arbitrator will decide.

State Sen. John Liu, a UFT ally who sponsored the law, acknowledged the obstacles but said the DOE has until 2028 to hire additional teachers for smaller classes and to build new schools to ease overcrowding — a big problem in his Queens district.

“The Department of Education has five years to get this right,” Liu said. “They need to hop on it.”

DOE officials did not respond to a request for comment.