The Anne Arundel County school system has reached a tentative settlement, including payment of about $30,000 in legal costs to civil liberties lawyers to avert retrial of a case in which administrators at an elementary school in Annapolis were accused of singling out black pupils for punishment and isolating them in storage closets.

Officials in the case said the proposed settlement, in which the county does not admit misconduct, includes an agreement that it will not isolate children in school rooms as part of its disciplinary program.

It also includes an agreement to pay about $30,000 in fees and expenses to the five attorneys who represented five black children and their parents in a $17 million lawsuit filed in federal court in Baltimore in 1981 against the county and administrators at Germantown Elementary School.

John Wisthoff, president of the county Board of Education, said yesterday he understood the settlement had been reached "in principle" and authorities were awaiting an agreement by the county's insurance companies to cover the $30,000 payout to the five lawyers.

The tentative settlement, which must be approved by U.S. District Court Judge Walter E. Black Jr., "satisfies our clients very well," said American Civil Liberties Union attorney Barbara Mello. "Their motivation in this whole thing was to keep other children from getting in this situation." Mello and county officials said they hoped Black will sign off on the settlement next week.

The case went to trial last November before Judge Black but ended in a hung jury. Attorneys for the children at first sought a new trial but then began negotiating with the county on a settlement.

The attorneys contended during the trial that Germantown's so-called "in-school suspension" practice was imposed discriminatorily against blacks and that several pupils were held in solitary confinement in dark unventilated storage rooms for up to five consecutive days during school hours. School officials acknowledged isolating the children but said they placed them in well-lighted rooms, gave them homework and checked on them every 15 to 20 minutes.