Students at a top public high school in Potomac, Md., hacked into the school’s computer system and changed class grades, and officials are investigating how widespread the damage might be, reports the Washington Post. The incident prompted an emergency staff meeting at Churchill High School and a recorded phone message to parents on Jan. 27. The extent of the apparent security breach was not immediately clear; teachers at the school were being asked to review their grades for discrepancies. The students involved used a computer program to capture passwords from at least one teacher, according to sources familiar with the situation who spoke on the condition of anonymity. Teachers were told to check grades for anomalies and correct them before first semester report cards are released Feb. 3, according to the sources. But because teachers at the school no longer keep separate records for their grades, it might be difficult to go back and find a student’s original grade, the sources said. School officials urged Churchill teachers to change their passwords immediately and rotate them more often. The 2,100-student school has a 98-percent graduation rate, 11 points higher than Montgomery County as a whole. Its average SAT scores were 1820 out of a possible 2400 in the 2008-09 school year, the second highest in the county…