Every time Elly Kluge's friends and colleagues ask what happened last week at the Advanced Placement European history test grading session in Colorado, the 67-year-old Arlington County history teacher says: "I was sent home early because I am a terrorist."

That is not quite accurate, Kluge acknowledges, but she loves saying it because she wants to make a point.

Kluge is one of the most experienced AP history teachers and graders in the Washington area, but Educational Testing Service officials told her she had to stop reading exams, and pay her own way back to the airport, because she had only a Virginia driver's license to prove her identity. They insisted she show a second form of identification under a federal law meant to control immigration and protect homeland security.

"What does homeland security have to do with grading history tests?" asked Kluge, who flew back to the Washington area Friday after being turned away from the seven-day grading session in Fort Collins.

Blame for the incident is disputed by Kluge and ETS officials. But there is little doubt the events stemmed at least in part from a culture clash: federal security rules vs. a teacher who has spent the past 29 years at the most rule-averse public school in the region.