An ex-teacher from Texas is suing the 17-year-old student she was caught having sex with, describing his conduct as "extreme and outrageous".

Disgraced Corpus Christi local Tanya Ramirez, 31, says the teen secretly filmed a tryst they shared in July 2014 and "disseminated the video to numerous people and caused the video to be posted on YouTube".

"You can't have sex with someone and film it without their knowledge, and post it on the internet," Ramirez's lawyer, Annie Pratt, told the New York Daily News .

The former King High educator is also suing the teen’s mother for describing her as a "predator" after the woman, Kimberly Tademy, told the media that Ramirez made a habit of seducing her young charges.

Her lawyers will argue that Ms Tademy's allegations exposed Ramirez to "public hatred, contempt, ridicule, and financial injury, and impeached her honesty and integrity.

"Even though she is guilty of having sex with a student, the student was a consenting adult when it happened," Ms Pratt said.

"Had she not been a teacher, this would not have been a crime."

Ramirez, who was not "directly" teaching the child at the time, was hit with a second charge in September last year after being accused of having another improper relationship with a student.