The celebrated Boston charter City on a Hill is closing one of its schools and imposing budget cuts at another due to falling enrollments.

Once a shining star in the Boston charter school world, City on a Hill Charter School is facing a massive financial crisis, prompting trustees on Monday to enact a series of dramatic budget cuts: It will lay off 23 teachers, administrators, and other staffers at its Roxbury and New Bedford campuses and will close the New Bedford campus in June.

This is a really difficult decision and we don’t take it lightly,” said Cara Stillings-Candal, chair of the trustees in an interview following their Monday morning board meeting. “We wouldn’t have made these decisions if it wasn’t in the best interest of families and students.”

The sweeping budget cuts represent the latest turbulent turn for the nearly 25-year-old charter school, which has been struggling with high leadership turnover, lackluster academic performance, and financial woes. Earlier this year, state officials placed the New Bedford campus on probation, and a year earlier teachers at all three sites unionized, a rarity for independent charter schools, which place a premium on operational autonomy.

The severity of this fall’s financial crisis emerged after headcounts at the three campuses revealed enrollment had dropped for a second year in a row. That, in turn, will lead to a loss of hundreds of thousands of dollars in per-student aid from the state and federal governments. The three campuses operate as independent schools overseen by a single board of trustees and an executive team.

Just 570 students are currently enrolled in grades 9-12 across City on a Hill’s three campuses, leaving 270 seats empty. The Boston campuses receive about $20,000 per student in state aid and the New Bedford site gets about $15,000 per student. Last year’s enrollment drop resulted in an $842,000 loss in state and federal aid.

The decline in charter enrollments mirrors a trend seen in a few states, like Michigan, where charters have lost their luster.