Comptroller Scott Stringer placed three city agencies on a new “watch list” Friday, saying he’s very concerned about their escalating spending.

Stringer rolled out the list — which targets the Department of Homeless Services, Department of Education and Department of Correction — while releasing an analysis of Mayor Bill de Blasio’s $88.7 billion preliminary budget for fiscal year 2019.

“These are the city agencies [that] appear to be spending more without measurable results, and I am calling on the mayor to undertake real evaluations of the spending,” said the comptroller, speaking at his Lower Manhattan office.

Stringer said citywide spending to combat the homeless crisis has more than doubled from $1.1 billion in fiscal 2013 to a projected $2.6 billion in 2019. Despite the increased investment, the shelter population has increased from 49,673 to 61,029.

Stringer also red-flagged the school system, where he found central administration staff has soared by 24 percent since 2012 — double the 12 percent rate of teachers.

Turning to jails, Stringer said it is troubling that inmate population is down while spending and violence and costs are up.

The cost of housing an inmate at Rikers Island has gone from $117,000 a year in 2008 to $270,000 in 2017 as the average daily inmate population dropped by 30 percent. Meanwhile, the number of violent incidents against both inmates and correction officers has tripled over the period.

Overall, Stringer also said spending is expected to increase at a rate of 2.6 percent annually through 2022 while city revenues are only projected to rise 2.2 percent over that period. He said that will result in budget gaps that grow to $2.2 billion for fiscal 2020.

Mayoral spokesman Eric Phillips defended the extra spending at the three agencies.

“The mayor’s made dramatic investments in homeless outreach, our schools, and our corrections system. They have helped lead the city to records in job creation, test scores, and crime prevention. We appreciate the comptroller highlighting these gains,” he said.