St. Mary's County School Superintendent Patricia M. Richardson said yesterday that she will resign at the end of December to take a job at the University of Maryland.

Richardson has been an educator in St. Mary's for 32 years, including eight years as superintendent of the 16,000-student Southern Maryland school system. She described her move to higher education as a homecoming -- returning to work in College Park, the city where she was raised, at the university where she received her bachelor's, master's and doctoral degrees in education.

"I've always had a relationship with the University of Maryland," she said. "I wanted to go while I still loved my job and look forward to coming to work every day." Richardson said she will head a graduate program in education, focusing on leadership training for teachers and administrators.

St. Mary's school officials praised Richardson's performance as superintendent, citing her work on a long-term funding agreement with the county, increased enrollment in Advanced Placement courses and her caring leadership style. Board of Education members said they probably would appoint an interim superintendent after Richardson leaves while they search for a permanent replacement.

"This was a surprise for me and the board, without question," said Salvatore L. Raspa, vice chairman of the school board. He said Richardson told the board Wednesday.

Richardson, 54, began her career in 1972 as a third-grade teacher at Piney Point Elementary School. After 10 years in the classroom, she became principal at Lettie Marshall Dent Elementary School in Mechanicsville. She was named acting superintendent in 1996, and the "acting" was removed from her title the next year.

This year, the school district agreed to a five-year funding plan with the county Board of Commissioners, making St. Mary's the first county in the state to make such a commitment. During her tenure, the district increased the number of Advanced Placement classes offered, from five to 21, and the number of students enrolled in those classes, from 170 to 1,371, according to school officials.

Richardson, who is married and has two children, both of whom are elementary school teachers in St. Mary's, said the stressful post at times took a toll on herself and her family.

In the past, community members have criticized the school system for not doing more to decrease the achievement gap between white and minority students and for not being more open to input from the community. But several people said Richardson's commitment to students and education never wavered.

"And she is one of the most charming individuals I've ever met," said Clare Whitbeck, a community activist and school board candidate. "If she takes a half-hour and focuses on you, it feels like you've just gotten a suntan. That's her gift."

"I wanted to go while I still loved my job," Patricia M. Richardson said.