Arlington County superintendent Patrick K. Murphy proposed a $520 million spending plan Thursday that would increase employee salaries while eliminating about 60 positions, including custodians, special education assistants, and employees working with teen parents.

The high-performing school system continues to grapple with a surge in enrollment and sluggish revenue growth. School officials expect to add nearly 1,000 new students next year, driving enrollment past 23,500.

Murphy said his top priority is rewarding employees and maintaining quality instruction. “Our staff is working extremely hard,” he said.

The proposal, a 4 percent increase over the current year’s spending, includes $7.2 million for step increases that range from 1.5 to 5 percent.

Employees earned a 2 percent cost of living net increase this year. This would be their first full step up the salary scale in two years.

Some of the increased spending would come from a proposed tax increase. The proposal also would save money by consolidating separately housed alternative programs for teenaged mothers as well as students who are pursuing diplomas through night classes or a more flexible program. Those services would move to the Arlington Career Center, where they would share administrators and support services and have access to more courses.

The plan also eliminates positions for three high-school gifted teachers and five special education assistants. Fifteen custodial positions are expected to be phased out through attrition.

Murphy is requesting funding for some new positions as well, including a security coordinator who would oversee emergency preparedness and a “residency verification specialist” who would investigate out-of-boundary students attending county schools. He also hopes to fund two drop-out coordinators to help at-risk students make it to graduation.

Extra budget pressures could come from federal or local spending cuts tied to sequestration, though potential impacts are still unclear, school officials said.

A public hearing on the superintendent’s proposal is scheduled for March 21. The final budget will be adopted in early May.