Arlington Public Schools chief Patrick K. Murphy announced Friday he is retiring from the role he has held for a decade leading the high-performing Northern Virginia school system.

During his tenure, Murphy oversaw school openings and expansions needed to contend with dramatic growth in the school system — enrollment has increased by more than 7,000 students since the 2009-2010 school year and exceeds 27,430, according to state data.

School system officials credited Murphy in a news release with increasing the graduation rate by 10 percent. During the past four school years, the system has earned full accreditation for all of its schools, a distinction given by the Virginia Department of Education that is used as a measure of school performance.

Murphy’s last day is expected to be Sept. 3. The Arlington School Board is beginning the search for a new superintendent, according to the school system.

In a letter to School Board officials, Murphy reflected on his more than 30 years in public education in Virginia.

He started as an educator in 1988 and was an assistant superintendent with Fairfax County Public Schools before starting in Arlington. He served as a principal at schools in Alexandria and Springfield.

Arlington County Superintendent Patrick K. Murphy will retire in September, he announced Friday. (Arlington Public Schools)

“I have come to a crossroad in my professional journey and believe that it is time for me to make a transition,” said Murphy, a Northern Virginia native. “As I think about the ebb and flow of changes that have occurred over the past 10 years, the progress we have made for children has been most rewarding. Each year we offer new opportunities to allow children to flourish, grow and reach for new heights of success.”

Murphy was named the 2015 Virginia Superintendent of the Year by the Virginia Association of School Superintendents. The association lauded the Arlington schools chief for curbing the dropout rate and increasing the number of students in the county who completed algebra and geometry by eighth grade.

School Board Chairman Reid Goldstein said Murphy guided the system through a period of unprecedented growth.

Goldstein said that under Murphy’s leadership, “Arlington’s reputation among Virginia’s top school divisions” was solidified.

“We thank him for his leadership and unwavering commitment to our students and their success,” Goldstein said in a statement, adding that Arlington’s school system “is in a very strong position, and we are poised to continue that success in the future.”