Student test scores at an acclaimed District of Columbia school fell sharply after testing oversight was beefed up, a TV documentary to be aired Tuesday found. The hourlong \"Frontline\" documentary, \"The Education of Michelle Rhee,\" raises questions about whether district officials adequately investigated suspicions public school employees may have altered standardized test answers while Rhee was chancellor from 2007-2010, The Washington Post reported. Adell Cothorne, principal at Noyes Education Campus during the 2010-11 school year, told \"Frontline\" she once saw three staff members at night in a room with more than 200 completed test booklets. She said one held an eraser and the other two had booklets open in front of them \"One staff member said to me, in a lighthearted sort of way, \'Oh, principal, I can\'t believe this kid drew a spider on the test and I have to erase it,\'\" Cothorne told \"Frontline.\" The Post said it marked the first direct testimony about potential tampering with answer sheets in D.C. schools. Cothorne said she reported the incident to the administration, but she knew of no action being taken by officials School district officials said Friday they could not comment on Cotherne\'s allegations because they had not seen the documentary, the Post said. \"Broadly speaking, reports about testing impropriety are taken very seriously,\" schools spokeswoman Melissa Salmanowitz said in an email. \"We have investigated and taken appropriate action for every instance reported to us.\" After Rhee left the district, she started Students First, which lobbies nationally for educational reforms she pursued at the Washington schools.