For more than a year, Kathy Francis kept her struggles with Arlington County Superintendent Patrick K. Murphy to herself. And then on Tuesday, exhausted and demoralized, the principal of Williamsburg Middle School let the world know, firing off a sharply worded, 1,700-word resignation e-mail to 1,200 parents and teachers.

That letter blames Murphy for preventing the dismissal of an employee whom she did not name but called "incompetent" and "a safety concern." Francis wrote that she tried for two years to fire the employee, who eventually was transferred to another Arlington school.

The missive, which quickly went viral in a community not accustomed to such unguarded talk about sensitive school matters, led some to question Murphy's leadership and others to affirm their support for the superintendent.

But as Francis attempts to plot a new future - she's barred by the school district from returning to Williamsburg, she said - many in Arlington are left wondering about her accusations and about what has the school system has done to address them. Some called for an investigation.

"We're not happy if there really was a security issue that this person is still in an [Arlington] school," said Lynn Pollack, a Williamsburg PTA member. "Nobody has a clue who it is. . . . People are just putting out guesses."

Arlington officials would not comment on the personnel matter. Arlington public schools "will continue to respond with a higher level of professionalism," officials wrote in an e-mail to the Washington Post.

School Board members and many parents, meanwhile, have voiced support for Murphy, who took over as superintendent in 2009. He was chosen as superintendent after a four-year stint as assistant superintendent of accountability for Fairfax County schools.

"I have full confidence in his leadership," said Abby Raphael, the School Board's vice chairman, who also has a child at Williamsburg, which she called "a terrific school."

Yet in the absence of an official explanation by the school system, the account by Francis, which she expanded on during an interview with the Post this week, is the only one available.

In the interview, she again declined to name the employee or provide details about his or her alleged misdeeds other than to say that the employee intimidated students in verbal exchanges and once threatened a co-worker. "But there was never any real interest in firing the person," Francis said in an interview.

Francis said the confrontation, which played out over many months, soured her relationship with Murphy and led to her receiving an "unsatisfactory" rating for the first time in her career. That came as school test scores among some sub-populations increased sharply. Scores overall remained fairly level but remained higher than the average for the Arlington school system.

"It's not your scores; it's your leadership," she recalled Murphy telling her. In 2009 and 2010, the school did not make adequate yearly progress, a federal standard required by the No Child Left Behind Act.

Francis said she tried to resolve the dispute through conventional channels but ran into bureaucratic hurdles. "The resignation letter seemed like the only way to let people know how terrible things had become," she said.

But the letter, which outlined in general terms the nature of Francis's concerns, sparked unease among some Arlington parents.

"I'm shocked and dismayed by Ms. Francis's allegations about the new superintendent. If even half of what she wrote is true, the schools are in trouble," said Joanne Marshall, whose daughter is in sixth grade at Williamsburg.

Another parent with a sixth-grade daughter at the school, Anne Paris, said,"Arlington's School Board should seek an independent investigation by an experienced outside law firm of the points raised by Ms. Francis - particularly as to the transfer of a potentially dangerous teacher and an environment of retaliation."

Last weekend, as Francis crafted the e-mail in an emotional, two-day push, she felt relieved to get her saga down on paper. "I was nervous, until my finger was hovering over the send button, but wanted my staff to understand what happened."

On Wednesday afternoon, members of that staff carried bouquets to Francis's home, and the 33-year public school veteran teared up. "They're all concerned," she said. "They're all so supportive."