Confidential information about hundreds of Fairfax County high school students was leaked and posted online, where the information remained Thursday night as the school system and city police started an investigation.

The names, student identification numbers and several grades earned by students at Fairfax High School were posted on a website, grouped by course. The leak involves ninth-through-11th-grade students, displaying their final exam grades, fourth-quarter grades and final grades for the 2011-12 school year.

Schools Superintendent Jack Dale said he was unaware of how the website, dubbed Fairfax Underground, obtained the students' personal information. The school system has asked the website to remove the information but has yet to receive a response. In addition to conducting a full investigation, Dale said he would take further action if the website does not comply.

"Violations of student privacy will not be tolerated and those who are responsible for this breach will be held accountable," Dale said in a letter to parents.

Fairfax City police are working with the school system's information technology staff to track the responsible parties.

Home addresses and Social Security numbers were not among the details leaked. "We have no reason to believe that this incident poses any threat to your student and do not believe you need to take any action," Dale said in his letter.

Still, parents expressed horror that their children's privacy had been violated.

"It's heinous that students, who are kids, minors, have their private information out there," said Inge Gedo, whose son's grades were leaked. "I don't know why someone would choose to do that."

Fairfax Underground bills itself as "a project site designed to improve communication between residents of Fairfax County, VA. Feel free to post anything Northern Virginia residents would find interesting."

The thread remained lively Thursday evening, as some posters said they were owed this information as Fairfax County taxpayers. One commenter, identifying as a parent, replied, "You absolutely have no right to that confidential information regardless of what taxes you pay."

Another wrote, "Someone at [Fairfax County Public Schools] is gonna get it bad for this. How could they allow this info to fall into the wrong hands?"