When Alexandria school administrators sit down to chart the future of their school system this year, the one issue public school officials fear most -- school closings -- will be near the top of the agenda.

Although no closures are planned for the coming year, Superintendent Robert W. Peebles said this week that the issue is nonetheless one the school system must face as student enrollment continues to dwindle and tight budgets get ever tighter.

"It may not be necessary in the next two or three years, but if enrollment continues to decline, even at a slow rate, school closings will probably be inevitable," said Peebles, discussing the administration's plans for a major evaluation of the school system.

Spurred by a citywide population drop, the number of students enrolled in Alexandria schools has fallen from 17,500 in 1970 to 10,500 currently. Seven schools have been closed during the past decade with the last group closing in 1979. Although recent declines have not been as rapid as in previous years, school administrators say they do not expect enrollment to level off until at least 1985.

"It's easy to plan when enrollment keeps going up, but when it begins to decline it's difficult to project just where we're going to be. There are so many other factors involved," said James Akin, assistant superintendent for planning, who blamed much of the student enrollment losses on condominium conversions in the city.

Families, Akins said, move out and are usually replaced by young professionals -- without children. Thus, the city's student stock is further reduced because of the declining availability of moderate- or low-income rental housing. Since 1973, nearly 20 percent of the city's rental stock -- or 3,720 units -- has been converted to or sold as condominiums, according to the city's planning office.

Although Akin expects the condominium conversion drain to continue, he stressed that school closings are not a foregone conclusion. Among other alternatives to be considered, Akin said, will be paring down course offerings and transferring students from schools with large enrollments to those with smaller ones.

"We are at a crossroads when we need to decide what we can afford and what we're willing to do without. We must determine the affordability of our goals," Akin said.

In addition to school closings, a number of items will be discussed during the school system's planning sessions, including the evaluations of adminstrators and teachers, as well as exams and academic standards. Tests which rely on memory and "robot learning," Peebles said, should be replaced by those which require the student to think.

"Looking back over the last 20 years, I think we (school administrators) have unintentionally become slack in what we expect students to learn," Peebles said. "The standards are there, it's just a matter of living up to them."

One of the first steps toward improving these standards, Peebles said, will be tried out in selected schools this year. Based on a pilot project at Charles Barrett Elementary School, student test scores will be stored in a computer and monitored by the student's teacher and principal before they approve advancement to the next level of learning. This method, said Peebles, should radically decrease the number of students whose learning problems go unnoticed.