(NewsNation) — Enrollment declines are putting thousands of schools across the country at risk of closing, according to exclusive data from the Brookings Institute.

First reported by The 74, data shows districts across the nation are making difficult decisions about whether they can keep schools open with fewer students enrolled.

Data shows 12% of elementary schools and 9% of middle schools lost at least a fifth of students over a four-year period. The South saw the biggest share of schools with declining student populations, but major urban areas including Los Angeles and New York also reported declines.

Even when schools don’t close their doors, declining enrollment can impact students. Districts may merge classrooms, lay off employees and cut expensive programs, including sports. Small schools are less likely to have classes like art and music and are also less likely to have advanced classes.

In California, more than 1,400 schools have seen a 20% or more drop in enrollment. Factors include parents moving children to private or charter schools along with demographic changes, including declining birth rates and high cost of living driving families out of urban areas.

Efforts to combat the decline include reaching out to families and students who have become disengaged with education, especially since the pandemic. Other districts are hoping efforts to promote affordable housing will help bring families back into neighborhoods with declining enrollment, though such efforts are often blocked by property owners.

Minority and low-income districts are more impacted by declines than middle-class ones, but in some cases communities have rallied to keep struggling schools open.

That may not last, however, as the trend is projected to continue over the next decade.