Nearly 1.7 million New Yorkers — or 1 in every 5 city residents — lived below the poverty line between 2011 and 2015, the largest number seen in the city since 1970, according to a report by the NYU Furman Center, released Wednesday.

And of those residents, children under 18 were more likely to be living in poverty than any other age group, with 535,700 kids, or roughly 30 percent of the city’s youth in poverty.

There is a strong “negative correlation” between school quality and neighborhood poverty rates, and Hispanics were the hardest hit ethnic group with 28.9 percent living in poverty during that time period, according to the report.

“The trend we see across the country is that poor children who live in high poverty neighborhoods don’t have good access to schools and it poses a barrier of upward mobilization to the next generation,” Furman faculty director Kathy O’Regan said.

A key contributor to the children poverty levels was the ability of parents to give their children access to better living conditions and resources, according to O’Regan.

“If you think about it from the other side, the non-poor families with children use their resources to avoid those [poor] neighborhoods when they have them,” she said.

The families face a bigger problem because more and more neighborhoods are filling up with residents who are under the poverty threshold, according to the report. The Furman Center pinpointed several neighborhoods throughout the five boroughs that saw jumps in poverty concentration.

More than 52 percent of neighborhoods in the Bronx were experiencing high or extreme poverty, making it the borough with the most locations living in poor conditions.

A neighborhood is considered in extreme poverty if more than 40 percent of its residents are poor.

The trend in growing numbers of impoverished children is seen across the entire country, where 22.4 percent of people under 18 are poor, after a decrease at the beginning of the century, O’Regan said.

She said the problem is amplified in New York because the population is so big.

“Sometimes we look at the rate that we forget the magnitude of the population,” she said.

The report was compiled using U.S. Census and American Community Survey data. Poverty level depends on the number and age of household members. For example, a household with two children and two adults was considered to be living below the poverty line if their annual income was less than $24,036.

On a year-over-year level though, there have been recent signs of improvement, O’Regan said. A report released by the mayor’s office last month found that city’s poverty rate went from 20.6 percent in 2014 to 19.9 percent in 2015.

Olivia Lapeyrolerie, a spokeswoman for Mayor Bill de Blasio, said the mayor is committed to tackling the issue.

“While there is still more work to do, this report reinforces the need to take aim at inequality by pushing for more affordable housing, better job opportunities, universal pre-k, community policing and access to quality health care,” Lapeyrolerie said in a statement.

O’Regan said the city should continue to make investments in affordable housing options throughout the five boroughs and increase investment in schools to keep combating the crisis.

“Those are classic levers that have been discussed,” she said.