This Sunday, a 53-year-old Fairfax County employe will trade in his tiny office in the county school headquarters for a spot among the ranks of the nation's unemployed.

That doesn't mean he's likely to end up collecting unemployment. For starters, he'll receive a check for $15,000 on Tuesday. Then, on Jan. 2, he'll receive another for $60,000.

The recipient is Linton Deck, who until June was superintendent of the Fairfax County school system, the largest in the area. The source of the largesse is none other than his former employer, the county school board, which hired Deck to be superintendent with great hopes in January 1980 and now is relieved to see him go.

The payments, which the board considers a good deal, are part of an agreement that enabled the board in June to buy out the last three years of Deck's four-year contract. That ended a tumultuous 2 1/2-year relationship that saw Deck abruptly resign after being pressured to do so by board members.

The problems were major differences over how the school system should be run and the board's frustration with Deck's poor record in community and board relations.

Deck agreed to continue working for the school system until this Sunday to help with the management transition. In the meantime, he has continued to draw his $68,280-a-year salary and a $4,860 travel allowance for use of his car and to have the premiums for his full health and life insurance coverage paid by the school board.

How has the transition been going? Deck, whose cool-at-best relationship with the press rivaled his relationship with the community, declined to say. "I'm no longer a public figure," was the only comment Deck relayed through his secretary to the county school's spokesman George F. Hamel last week.

"I haven't seen him in, oh, I guess, 10 days," said Hamel, whose office is just down the hall from Deck's.

"He's been traveling a lot lately," Dottie DeVall, Deck's secretary, said Friday. "He won't be in physically more than half a day between now and next week."

School Board member Chuck Caputo said the payoff and work arrangement aren't unreasonable "when you consider the realm of what we might have had to pay." Under the contract, Deck could have been entitled to another year's salary.

Privately, some school board members have said the 3 1/2-month delay between his resignation and departure was intended to give Deck time to find another job.

Colleagues close to Deck say he's spent much of the past several weeks job hunting and doing various education consulting work. Deck reportedly has received and turned down several job offers.

Part of his time has been taken up as a senior fellow at Vanderbilt University in Nashville, where Deck is helping to develop a program for training school superintendents, a university spokesman said. The job, which began in September and continues through the current academic year, requires Deck to be in Nashville two days every two weeks, the spokesman said. He described the pay as "a modest sum."

He said senior fellow positions are reserved for nationally known experts in various fields. Deck served as an assistant superintendent of the Nashville public school system from 1969 to 1971.

Although Deck kept his salary when he resigned as superintendent, he was forced to move out of his spacious office; he now works in a small, modest office. His secretary DuVall, who moved with him, will pack up and move back down the hall next week as secretary to the new superintendent, William J. Burkholder.

As for Deck's immediate plans: "He will stay in the area," Hamel said. "He's got a lot of consulting work lined up and he's got those cash payments coming."