Melissa Bonkoski
Melissa Bonkoski, 38, was re-arrested Tuesday for allegedly sexually assaulting a student. Police handout

A science teacher has been re-arrested after new information revealed that the teacher did have sex with a 16-year-old pupil she had "harassed" with text messages.

Melissa Bonkoski was arrested in July on sexual assault charges after an alleged relationship with a male student.

The 38-year-old science teacher and softball coach at Owen J. Roberts High School in Pottstown, Pennsylvania, was re-arrested and charged on 12 felony counts on Tuesday (29 August).

Authorities say they received new information about the extent of her alleged sexual relationship with the student.

"Rule No. 1 if you are a teacher or a coach: Do not have sex with a student," Chester County District Attorney Tom Hogan said according to NBC.

"Breaking this rule is a one-way ticket to arrest, losing your job, and prison, not to mention profound damage to the victim and the school community which you were entrusted to serve."

A criminal complaint said detectives became aware of the allegations in March when the now 16-year-old student told them he was being harassed by Bonkoski.

The messages were said to have begun in December 2015 and after a while Bonkoski told police she used a throw-away phone to communicate with the boy believing it could not be traced to her: "I thought I was being smart," she told police.

In an interview with police in July Bonkoski told investigators that the pair had kissed three to four times in a car, discussed sex, and the boy had slept in her bed.

Then in an 11 August interview, Bonkoski told police that she did have sex with the victim after they watched television at her house, according to reports.

All sexual contact ceased in January this year, according to Bonkoski, with the alleged victim admitting he was upset he had cheated on his girlfriend.

The Daily Mail reported that the victim's girlfriend told police of messages that she had found on his phone.

The charges against her include three counts of institutional sexual assault, three counts of unlawful contact with a minor, one count of corruption of minors and one count of criminal use of a communication facility.

Bonkoski has resigned from her teaching role, according to reports.