The Montgomery County Board of Education agreed this week to formally hear the complaints of parents protesting the closing of Harmony Hills Elementary School, while stressing that the March 22 meeting should not give parents "any particular expectation" that the schools will not be closed as planned.

"We're delighted," said Charles Billups, president of the Harmony Hills Parents-Teachers Association. "We have never had the opportunity to make ourselves heard before. Now we have to convince the board members" to rescind the closure order, he said.

Harmony Hills is scheduled to be closed this June, with its remaining student population diverted to other schools in the so-called Aspen Hill cluster. The scheduled closing would bring to 24 the number of county schools closed recently because of changing - mainly declining - enrollment patterns.

Twenty-two of the 24 schools have been closed within the last three years.

The board's action follows a weekend protest and sit-in staged at the school by dozens of angry parents, many of them pushing baby carriages and carrying placards. At Tuesday's meeting more than two dozen persons showed up to lend support to the reconsideration effort.

The motion to hold a formal hearing on the Harmony Hills matter was offered by Blair G. Ewing. Voting in favor of it were Ewing, Herbert D. Bennington, Marian L. Greenblatt and Roscoe R. Nix. Voting against it were board president Elizabeth W. Spencer, Daryl W. Shaw and Verna M. Fletcher.

"If we can convince Mrs. Fletcher we can convince anyone," Billups said after the meeting.

According to George Fisher, the school system's director of planning, the recommendation to close Harmony Hills was one of several submitted to the board by Superintendent Charles M. Bernardo last Dec. 13.

"We had to look at the entire Aspen Hill cluster, and not just Harmony Hills," Fisher said. "The fact that it may have had less of an enrollment decline than other schools doesn't compensate for the fact that the cluster as a whole is losing population."

These are the schools in the Aspen Hill cluster: Flower Valley, North Lake, Barnsley, English Manor, Rock Creek Valley, Harmony Hills, Aspen Hill, Wheaton Woods and Brookhaven. The current combined enrollment of 3,819 is expected to drop to about 2,900 in 1982; Fisher said.

Also slated for closure from this cluster is the Aspen Hill Elementary School. Fisher said that no parents from Aspen Hill had protested to the board "so far".