With a change of one letter, parents at Northern High School have set off a bitter struggle among Calvert County parent-teacher organizations.

Members of the Parent Teacher Student Association (PTSA) at Northern voted last month to dissolve their group and reorganize as a Parent Teacher Student Organization (PTSO). The difference? The new group is not affiliated with the national PTA and therefore does not pay dues to the PTA or follow its rules.

County PTA officials have refused to recognize the new group at Northern.

"As far as we're concerned, that PTA is inactive, not dissolved," said Rose C. Crunkleton, president of the Calvert County Council of PTAs. Crunkleton said she is looking for parents to serve as officers of the Northern PTA chapter even as the new parent group there continues to meet.

Northern High is the second Calvert PTA chapter in as many years to disband and form an independent parent group. Last year, parents at Sunderland Elementary voted to leave the PTA and create the Sunderland Family and School Organization.

The schools are part of a nationwide trend of parents leaving the PTA, whose membership has declined from a high of 12.1 million members in 1963 to 5.9 million last year. Today, fewer than one in four schools -- in kindergarten through the 12th grade -- have a PTA or PTSA, the groups affiliated with the national association.

Wendy Miller, president of the Northern PTSO, said parents were tired of paying dues to the state and national PTA when those funds could have been used at the school.

"For every $5 membership, we paid $3.55 in dues," Miller said.

At Northern's open house last month, Miller called for a vote to defect from the national PTA and form a new group. A county PTA official handed out fliers titled "Why Stay PTA?" that were intended to persuade parents not to leave the national association.

Still, the parents decided to disband the PTA chapter. Crunkleton called the vote "null and void" and said Miller violated the PTA's bylaws. Miller did not give 30 days' notice of the meeting and allowed parents who joined the group minutes earlier to vote, Crunkleton said.

"You can't have people coming up off the street signing up to join their organization and dissolve the PTA," she said. "We don't see it as a valid vote."

Miller declined to comment about the vote, saying she did not want to further inflame tensions.

At Sunderland, parents said they are pleased with their decision to leave the PTA.

Kathleen Roberts, president of the Sunderland FSO, said the group sent $825 of its $1,625 in dues to the national and state PTA. Now, it is able to use that money in the school. For the first time this year, the group gave $500 to Sunderland's physical education program, Roberts said.

"I'm very proud of our parents that we went ahead to go and make this change," she said.

Crunkleton said the new groups ignore the important benefits of the PTA. She said dues to the group are used to lobby elected officials at the county, state and national levels to improve education. The PTA also provides lower liability insurance rates and an important support network, she said.

"When you're a [non-PTA group], you're an isolated school," Crunkleton said. "It really is essential to be part of the community."

Students at Northern High and Sunderland Elementary may be blocked from participating in Reflections, a PTA-sponsored arts recognition program, said Marianne Roberts, the program's chairman. Roberts said she has received complaints from two Northern parents that their children might be barred from participating.

But many Northern parents said the entire debate seemed academic.

"I stay out of the PTA and the PTSO," said Rebecca Beeman of North Beach, whose son is an 11th-grader at Northern. "I think they are kind of worthless."

Board of Education member Mary D. Garvey said she hoped the conflict would not distract parents from more important issues.

"It's a shame that this big war is going on," said Garvey, a former PTA member. "All the parents are fighting against each other, and that can't possibly be good for the school."