Kelli Vassallo is accused of having lesbian relationships with two pupils
Kelli Vassallo, 36, faces charges after turning herself in to police following a seven-month probe.
She is said to have molested the younger of the two girls at least 20 times, starting when she was 13.
The brunette is also accused of having up to 50 sexual relations with another girl when she was 17 and 18 – and teaching her to drive.
Vassallo, a US teacher in the Williamsport Area School District, was seventh-grade girls basketball coach between 2012 and 2015 and assistant girls softball coach from 2011 to 2014 in the Loyalsock district.
Judge Marc Lovecchio approved her request for separate trials because he found there were no similarities between the two cases which occurred four years apart.
"That a 13-year-old may have been molested over a period of a year is far different from the other situation in which a 17-year-old essentially fell in love with the defendant and they had consensual sexual encounters," he said.
The assaults allegedly happened on the younger girl at the teacher's home and in a bedroom of another house she had access to.
Kelli Vassallo was a US teacher in the Williamsport Area School District
The pupil, who was on her basketball team, said the relationship started in June, 2013, with Vassallo texting her while "helping her through a rough time”.
Three months later, Vassallo reportedly told the teen: "I can't fight our feelings.
"I know it's wrong, but I think we should try to do this."
The teenager, now 16, told investigators she spent a lot of time at Vassallo's home in Loyalsock, Pennsylvania, doing "homosexual stuff”.
Touching led to kissing, showering together and finger penetration until August 2014, court files said.
The girl said Vassallo told her it would have to stop if people got suspicious.
She blew the whistle because "now that she's older, she realised what happened to her was not okay”.
Vassallo apparently met the older girl while the teen was babysitting for a family the teacher was living with.
They were said to have contacted each other by phone and through Facebook.
The relationship began in the autumn of 2009 with Vassallo giving the pupil gifts, investigators said.
But the girl's concerned parents found 275 texts between the two and drew up papers "preventing Vassallo from contacting their daughter.
"However, Vassallo continued the contact, using other people's phones and Facebook pages.
"The teen thought it was okay to still be talking with her since Vassallo was an adult and reaching out to her."
The following summer, the relationship between the two allegedly became physical, police were told.
The pupil, now in her early 20s, was quizzed by police in 2010 about a relationship with Vassallo. But she denied anything inappropriate happened and the case was closed.
Vassallo is out on bail charged with aggravated, institutional and indecent assault, corruption of minors and criminal use of a communications device.
The crimes allegedly happened while she was working for the Loyalsock Township School District.