Should Teachers Having Sex With 18-Year-Old Students Be Illegal?

Former high school teacher Brittni Nicole Colleps is shown during a recess in her trial in Fort Worth, Texas, in this Aug. 14, 2012 photo. (Ron T. Ennis/The Fort Worth Star-Telegram/AP Photo)

Former high school English teacher Brittni Colleps is serving five years in prison for having sex with five of her students - but unlike other teachers who wound up behind bars for having affairs with their underaged pupils, all of Colleps' teen sex partners were 18 or older.

Still, under Texas law, the sex acts made Colleps, 28 years old and the mother of three small children, a felon: The law prohibits any educator in a primary or secondary school from having sex with an enrolled student of any age.

Assistant District Attorney Elizabeth Beach prosecuted Colleps' case and defended the law in an interview with "20/20."

"Who has more power in the classroom?" she asked. "Does the teacher have more power or does the students have more power? The teacher has more power. And so the teacher can use that power to sexually exploit students in the classroom, even if those students are 18 years old."

Colleps disagrees, telling "20/20? correspondent Deborah Roberts in an exclusive interview that she feels she shouldn't have faced criminal charges for having sex with consenting adults. Watch the full interview on "20/20? Friday at 10 p.m. and vote below to tell us how you feel about the issue.