The plane's pilot, Franklin J.P. Augustus, was also killed in the Aug. 16 crash.
Aela Mansmann, a 15-year-old sophomore at Cape Elizabeth High School outside Portland, has been at odds with Cape Elizabeth Schools for a month
The defendant told a judge that the white substance he was caught with was powdered milk, but he pleaded guilty anyway to get out of jail.
Rossiter Elementary School in Helena was evacuated Tuesday morning after the item was found.
U.S. Customs and Border Protection says the couple "slowly and deliberately" drove across the border into Washington state.