A Prince William County associate school superintendent resigned Wednesday night after school officials completed an investigation into whether he was involved in falsifying teacher evaluations in neighboring Fairfax County.

Associate Superintendent John C. Randall Jr., who was principal at JEB Stuart High School in Fairfax in 1988 when performance ratings were lowered on the evaluation forms of three teachers, said yesterday that he had been forced to step down.

Randall said he did not change the evaluations.

Randall said in an interview yesterday that he felt he could continue to work with Superintendent Edward L. Kelly and the board.

"I should have been allowed to rise above this, instead of being taken down in one fell swoop," Randall said.

The lower evaluations in Fairfax had been retyped on new forms showing the signatures of both Randall and each of the teachers, Fairfax sources said. The teachers have said the signatures on the altered forms are not theirs, according to Fairfax sources.

Kelly confirmed that as part of Prince William's investigation, the school system hired a handwriting expert, who examined all the signatures on the altered forms. The expert reported that Randall's signature was on all the documents, school sources said.

"I have no knowledge of why there is a difference" in the evaluations, Randall said yesterday. As for why his signature appeared on the altered forms, Randall said, "I don't have an answer."

Fairfax officials discovered one altered evaluation form by chance in June, a year after Randall, 50, retired from the school system with 25 years of service, and became a principal in the Montgomery County school system.

Prompted by the discovery of the changed form, Fairfax officials conducted a districtwide probe of all teacher evaluation forms done in 1987-88 as part of the county's merit pay system and found two others at Stuart.

They concluded that the problem was limited to the three Stuart evaluations, which had been lowered, but not enough to affect the teachers' merit pay.

The school system held Randall responsible because he was the principal in charge at the time, placed a letter in his file and took no further action.

Representatives of both Fairfax teachers' unions said they believed the ratings had been reduced from "exemplary" to "skillful" because upper-level school officials had complained that too many high ratings were being given.

The Prince William School Board unanimously voted to accept Randall's resignation during a closed session late Wednesday night, members said. "Mr. Randall's problems were certainly not with us. He did a very fine job for us." said Board Chairman Maureen S. Caddigan.

Randall, who made $71,845 annually in Prince William, received no severance pay except his unused vacation time, Kelly said. School officials said there is no grievance procedure for upper-level administrators.

Kelly, who hired Randall earlier this year to oversee 20 Prince William schools and evaluate their principals, said he did not learn of the altered forms until a reporter called him last month.

Randall said he is baffled why the allegations surfaced publicly only recently. "Why so long," he said. There seems to be a conspiracy, he said, "to make an example . . . {of} one black administrator."

William Hundley, Prince William's only black School Board member, said that raising race in connection with the incident was "insulting."

Kelly launched an investigation late last month. On Friday, Kelly and Randall met to discuss the preliminary results, and Randall was asked for an explanation by Monday, both Kelly and Randall said.

After more information came in, Kelly said he again met with Randall on Wednesday and told him he was going to the board with the report. The former associate superintendent agreed to resign that afternoon.

"I think he wanted to get it over and done with," Randall said.

After Wednesday night's School Board meeting, Caddigan read a statement from Randall saying he had been "tarnished" by the allegations. "I cannot in fairness . . . continue in my role and meet the high expectations set forth by the superintendent and the staff," Randall's statement said.

The associate superintendent slot held by Randall will remain open for the remainder of the school year while the county seeks a replacement. Randall was the school system's highest ranking black male employee.