Two Fairfax County middle-school students used stolen passwords to wreak havoc with a school software application used countywide by thousands of teachers, students and parents, according to authorities.

Officials at Lake Braddock Secondary School in Burke reported the breach to police Jan. 3, the first day of classes after winter vacation. Course content had been erased from the school’s Blackboard site, an online system that teachers use to post assignments, hold discussions and communicate with parents.

The Blackboard system had also been used to send inappropriate messages to students that appeared to come from teachers, said Maribeth Luftglass, Fairfax’s assistant superintendent for information technology.

According to one Lake Braddock parent, Facebook began buzzing in late December with students’ complaints about the Blackboard-related oddities, including missing assignments and “poorly written pornographic e-mails” they received via the online system.

An investigation led to the two boys, who had apparently obtained the passwords of a fellow student and 17 teachers, Luftglass said. Officials don’t know how the boys got the passwords, but there is no evidence that they hacked into the Blackboard software or exploited a security loophole, she said.

Citing privacy laws, Luftglass declined to name the two students or describe what school disciplinary measures would be taken. Meanwhile, Fairfax police “take these allegations very seriously” and are considering whether to charge the boys, said spokeswoman Lucy Caldwell.

Blackboard is a Washington-based company that provides education software to K-12 school districts and colleges across the country. A spokesman said the company expects to fully restore the deleted data.

This is not the first time a Fairfax student has gotten into Blackboard trouble. In 2010, a third-grader deleted content and changed the passwords of administrators, including Superintendent Jack D. Dale.

An investigation revealed that the 9-year-old had used his teacher’s password to gain access to the system. Police at the time said the child was “very intelligent” and “had no criminal intent.” No charges were filed.