When Grace Baisinger of Washington became president of the National Parent Teachers Association last May, the leaders of the District's PTA organization gave her a telephone receiver shaped like Mickey Mouse.

To some of the PTA's critics the telephone symbolized the organization's problems.

"There's too much Mickey Mouse in the PTA already," one disaffected member said. "There are too many ceremonies, too many awards and plaques and pins. There's too little concentration on the issues of education."

Baisinger, who had the phone installed in her house on Arizona Terrace, NW, strongly rejects the criticism.

"Yes, we've had some problems," she said, "and our membership has gone down. But recently, the PTA has become more active, more advocacy-oriented than it used to be . . . We still want to work with the schools as partners, but I tell everyone now that there must be an equal partnership."

Since 1963 when PTA membership reached a peak of 12.1 million nationwide, the number of members has dropped almost in half - to just over 6.4 million last spring.

Only about a third of the nation's 88, 000 public schools now have PTA chapters that are affiliated with the national organization. Thousands of others have independent parent groups with no national ties. Others have no active parent groups at all.

The PTA's national magazine, which used to print more than 500,000 copies a month, stopped publishing three years ago because of substantial losses in circulation and revenue.

Its national staff, housed mostly in its Chicago headquarters, now is down to about 35, compared to a peak of 70.

Baisinger and other PTA leaders are trying to stop the decline. In the past year the organization has gotten wide publicity through its campaign against violence on television.It has also launched a program to get courses on parenthood taught in the schools, primarily as a means to discourage teenage pregnancies.

In September, the PTA opened a Washington office for lobbying. Next month it is sponsoring its first conference on urban schools. It is also trying to recruit members where it seldom looked for them before.

"Historically, certain groups - married parents, teachers, and students - have joined the PTA, and today this is still true," Baisinger wrote in a message to local PTA presidents. But to make your unit a truly dynamic force in the community, you should also seek out 'new' groups such as single parents, senior citizens, and business leaders. Anyone - and everyone - who cares about the lives of children and their education is a potential PTA member."

Yet, membership continues to go down. Last year the decline was 217,000, but Baisinger noted that this was the smallest yearly drop in more than a decade.

Why the PTA is loosing so many members is a subject of considerable debate.

PTA leaders say the main factors have been the drop in school enrollment, a rise in national PTA dues - still a modest 20 cents per member, the increase in single-parent homes because of divorces and the sharply increased proportion of women who work.

Women volunteers have been the mainstay of the PTA since it was founded in 1897 as the National Congress of Mothers, but as more women work, fewer volunteer for PTA activities.

Baisinger said PTA membership also has been cut by school consolidation and desegregation busing programs, both of which take children away from neighborhood schools.

"Many of the parents still want to come to the schools," she said, "but the schools aren't close by and they just can't drop in. Sometimes it takes so long to get there that it's difficult to become involved."

To the PTA's critics, though the organization's membership losses have stemmed mainly from what it does. "The PTA's biggest problem is that they haven't been a meaningul organization," said Dorothy Rich, director of the home and School Institute, a Washington-based group that teaches parents to teach their children after school. "In the face of adversity they're turning around now. But for too long they were a nice, nice organization where you could go to a bake sale but the concerns of parents weren't expressed.

"To a large extent they were run by teachers and principals," she continued. "They should have been a rallying point for parents who wanted change in the schools, but they weren't."

"Sometimes at PTA meetings they still don't get beyond the by-laws and the lists of life members, the pinning of pins, the lighting of candles, should like that," said Robert Boyd, executive director of D.C. Citizens for Better Public Education an activist education group here. "People who are serious about education just get tired of that. They want to get involved in substance."

Baisinger acknowledges some of the critics' points but says the PTA has changed. Until 1972, she said the group's national constitution contained a clause declaring that PTA's would "not interfere with the administration of schools." She said many principals took it as promise "to support school decisions, and not to try to change or question them."

The clause has been replaced, she said by a provision that PTAs "shall seek to participate in the decision making process establishing school policy." Local and state PTAs, she said, have become far more assertive with school officials even though teachers and principals still belong.

"We couldn't keep the old by-laws," Baisinger said. "The schools today have a generation of parents who were the children of the 1960s, who questioned all authority." These parents very definitely want meaninful participation."

In some ways, she said, the PTA is returning to the outlook of those who started it in 1897 as part of the progressive movement. According to one PTA pamphlet, the group in its early years was "an unabashedly political organization," campaigning for child labor laws, housing codes, and child welfare benefits, as well as for public kindergartens.

Baisinger, 55, is the wife of a Washington lawyer, and she has been a PTA member for 23 years since her daughter went to Stoddert Elementary School in Glover Park. Since 1966 she has been active in the national organization.

For the past six months she not only has criss-crossed the country on PTA business, but also visited China for 18 days as part of a delegation of American educators.

Her most conspicuous activities have dealt with the PTA project on TV violence.

At its convention last spring, the gruop voted to put the three television networks "on probation" to reduce the amount "gratuitous violence in their programs" by Jan. 1. Baisinger said PTA members now are monitoring network programs and the National organization plans to issue ratings of them in late January or February. If there in no "substantial response" by the networks, Baisinger said, the PTA has still kept largely clear of the country's most divisive educational issues: desegregation busing programs and effoms to set minimum high school graduation standards.

"We're a large very demorcratic organization, with a great diversity of people," Baisinger said, "not a small clitist group. We really believe in local control . . . in organization like us can't take on some issues. We just have to stay out and educate our members."