The investigation into Sandy Binkley began after a parent wondered why a teacher was sending her son a text message saying "I'll have to mark you absent," The (Nashville) Tennessean reported.

Binkley, who graduated from Portland High School in 1990, returned there to teach. She was popular with students and received glowing evaluations.

She married another teacher, Doug Binkley, now principal of an elementary school in Hendersonville. The couple, who have three children, are members of Cornerstone Church, a Pentecostal congregation.

But police now say Binkley had sex with the teens in a supply closet or off campus. She was charged in September with crimes involving two boys and then Oct. 1 with the third.

Assistant Police Chief Richard Smith said investigators are interviewing students and more charges are likely.

"A search of her classroom turned up some disturbing things," Smith said.