A pro-charter advocacy group is continuing to argue that the city’s schools have grown markedly less safe under Mayor Bill de Blasio, this time by revealing police data Friday that shows the number of weapons confiscated in schools jumped last year.

The report by Families for Excellent Schools, a staunch foe of the de Blasio administration, follow two separate incidents where students brought guns to city schools this week. The attention to school safety comes as the mayor tries to revamp the city’s school-discipline policies.

The data, which the city did not dispute, shows that the police recovered 1,678 weapons in the 2014-15 school year, an increase of 170 weapons from the previous year. (That included a significant spike in taser and stun gun recoveries.) The number of recovered weapons has been fluctuating since 2010 with the least weapons found in 2014, according to the data.

As part of its reevaluation of the city’s school discipline and safety policies, the de Blasio administration is looking into removing metal detectors from some schools. The increase in weapons could make it harder for the city to make the case for removal.

Education department officials said they work in close partnership with the city’s police department to swiftly address safety incidents.

“Schools must be safe havens for students, staff and families and there is absolutely zero-tolerance for any weapons in schools,” said department spokeswoman Toya Holness.

In two different incidents this week, students were caught with loaded guns in schools. In the first, a fifth-grader brought a gun to his Queens elementary school. Two days later, a 15-year-old carried a gun into a nearby high school. Neither school has a metal detector.

Meanwhile, the mayor and Schools Chancellor Carmen Fariña continue to push forward with discipline reforms.

This fall, de Blasio released a “roadmap” for changing school discipline that calls for the police department to determine where metal detectors can be eliminated or scaled back. Earlier this week at a city council hearing, Schools Chancellor Carmen Fariña said the city is still reviewing the use of metal detectors at some schools, and will make a decision by September.

Some advocates argue that the metal detectors are demoralizing to students of color, who are disproportionately subjected to them. Nearly half of all black high school students pass through metal detectors, compared with just 14 percent of white students, according to a recent WNYC analysis.

But many educators and parents argue that metal detectors are necessary to prevent dangerous weapons from entering schools.

The FES report could add fuel the second argument, and is designed to stoke concerns that de Blasio’s attempt to overhaul school discipline will jeopardize students’ safety.

“Mayor de Blasio’s refusal to confront the epidemic of violence in our schools is putting families across the city at risk,” said Jeremiah Kittredge, Chief Executive Officer of Families for Excellent Schools.

In a report that FES released in February, the group argued that state safety data shows that school safety incidents have increased under de Blasio. The group also paid for a series of television ads based on the data claiming that almost every public school child is exposed to school violence.

However, the city cited a different set of data that showed incidents has decreased. And the state education department quickly flagged the numbers highlighted by FES, saying the metric they are based on is problematic and under review.

United Federation of Teachers President Michael Mulgrew, de Blasio’s close ally who often trades fires with pro-charter groups, blasted FES in an op-ed Friday for using those statistics. In particular, he attacked the group for ignoring another trend that he said the data shows: that safety incidents increased more quickly from 2014 to 2015 in charter schools than district schools.

“If in fact the state numbers are not reliable,” he wrote in the New York Daily News, “then we are seeing yet another instance of charter advocates looking only at the numbers they want to see.”