The Radnor school district superintendent, Gary Cooper, who came under increasing fire in the last year for his management style and for approving a grade change for a high school student last fall without notifying the teacher, has resigned.

Cooper, 56, who was hired in 2004 to a five-year contract and was paid $198,450 this year, made the announcement at a school board meeting last night. His last day will be Aug. 31.

A statement issued by the district said Cooper was leaving because he had "decided to pursue other interests." Cooper said in the statement: "Radnor is an incredible school district, with a dedicated, productive staff and a wonderful student population. I will certainly miss working with all the administrators and employees - they are a top-notch group."

There was little comment at last night's meeting. School board president Kathy Fisher told Cooper: "I'd like to thank you very much for your dedication to this school district over the past three years. . . . We wish you really well in the future."

The last year has been a tumultuous one for the 3,675-student district, one of the highest-performing in the state, and Cooper has been the target of ire from several quarters.

Teachers' contract negotiations last summer and fall were acrimonious, with a threatened strike, and some teachers, including the union's leadership, said the superintendent's attitude toward them during and after the talks was partly responsible for strained relations. Radnor Township Education Association president Betsy McIlwain said in a statement that it was the union's "conviction that Dr. Cooper's resignation is appropriate."

Since June, eight administrators either have left or will soon be leaving, and in recent months several residents, saying they thought morale was low among the staff, asked the school board to launch an investigation to determine the cause of the exodus.

A cheating incident early this year in which 26 seniors and juniors were suspended for circulating the answers to an Advanced Placement test also roiled the district. And the arrest of senior Cameron Plaice last fall for allegedly writing threats on a restroom wall sparked a debate about tolerance and diversity after his defenders said he was responding to racist and anti-Semitic slurs.

Relations between the teachers and the administration were shaken again early this year when it became known that three grades of a high school student were changed by the principal last fall, with Cooper's approval and without the knowledge of the teacher involved.

The cheating and grade-change incidents are under investigation by the school board, which has set no timetable for releasing its findings.

Cooper was unavailable for comment before the meeting yesterday.

In recent interviews, he said that the union negotiations were difficult because last year was the first time in several contracts that the district had asked for substantial changes. He said the grade-changing incident, although not handled well, was an isolated occurrence and a new policy that included consulting teachers was being implemented.

Cooper said that administrators are leaving the district in large numbers because of the combination of a generous retirement incentive and individual career advancement opportunities. The cheating incident, he said, reflects the pressure on students attending a highly competitive school. And his management style, he said, includes frequent consultations with parents and teachers to get their opinions on important issues.

Cooper came to Radnor three years ago, replacing popular superintendent John DeFlaminis, who had run the district for 17 years. He came from the Frontier Central School District, near Buffalo. He has had a 29-year career as an educator, including stints in the Kennett Consolidated School District and the Souderton Area School District.

Radnor is the third high-profile district in the area to face a vacancy at the top. Lower Merion superintendent Jamie Savedoff is retiring next February and Haddonfield superintendent Joseph O'Brien is leaving the Haddonfield district this summer to take the reins at the Chester County Intermediate Unit.

Contact staff writer Dan Hardy at 610-701-7638 or dhardy@phillynews.com.