The private Georgetown Day School has received final approval from the District's Board of Zoning Adjustment to build a 410-student high school and athletic field off upper Wisconsin Avenue NW.

At the meeting last week, the board confirmed last month's 4-to-O vote to grant the special exception the school needs to build on the five-acre residentially zoned tract. But the BZA aproval is contingent on the school's compliance with 18 requirements, including one that it hire security guards when its parking lot is not in use and another prohibiting students from parking on surrounding residential streets.

Gladys Stern, Georgetown Day School director for 10 years, said she was "very pleased at the decision. We feel we complied with the law in every respect, and we intend to comply with all those things we've been asked to do."

The plan to build the high school and athletic field has split the surrounding neighborhood.

"We feel that we've been stepped on all over by the Board of Zoning Adjustment and Georgetown Day School," said Joseph Mascolo, head of Concerned Citizens of Friendship Tenley, a group that formed last year to oppose the school.

" . . . We have closed the file on this," Mascolo said last week. "We would like to fight this thing in court, but we don't have the money . . . and let's face it, Georgetown Day School has far more money than we do."

The opponents testified before the zoning board that the school, which would be built between River Road and 42nd, Chesapeake and 43rd streetsNW, wouldbring noise, litter, traffic and parking problems and represents an unwelcome intrusion into the quiet community.

Stern said construction will begin in November.

Meanwhile, members of Georgetown Day School's board of directors said there has been disagreement about the plan to close the high school on MacArthur Boulevard because it would result in a tuition increase that could decrease enrollment of middle-class and low-income students. The school now charges more than 5,000 a year. The board reached an unspecified compromise.