A 24-year-old teacher in the US has been charged with sexual assault after she allegedly had an inappropriate relationship with one of her 11-year-old students.

The teacher was identified as Madison Bergmann.

According to charging documents, police were called to River Crest Elementary School in Hudson "regarding inappropriate conduct between a current teacher and a 5th grade student" — an 11-year-old boy, reported CBS News.

Officers were presented with screenshots of multiple text conversations between the victim and Bergmann talking about their encounters, which allegedly occurred inside the classroom during lunch or after school, the news channel reported.

The incident came to light after the victim's mother took his phone.

She heard the victim talking over the phone with the teacher recently which forced her to take the device.

Charges say the victim told investigators that he talked to Bergmann "almost daily," and that he got her number when he went skiing with her and his mother at Afton Alps over winter break, reported CBS News

Inside Bergmann's backpack, an officer reports they found a folder with the victim's name on it containing many handwritten notes.

The victim later told police that he and Bergmann would write each other notes throughout the day. Many of the letters talk about the two kissing each other, court documents said as quoted by CBS News.

In one of the letters, Bergmann allegedly wrote as quoted by the news channel, "One of my cousins is in the 5th grade and I can't imagine a man talking to her how we talk. I know we have a special relationship and I do love you more than anyone in the world but I have to be the adult here and stop."

Principal expresses shock

Principal Kimberly Osterhues said the incident left him shocked and disturbed.

"We are shocked and disturbed by this news. Our greatest concern is for the River Crest School community and the children impacted," Principal Kimberly Osterhues wrote in a message to parents as quoted by CBS News.

The teacher was reportedly let out on a $25,000 signature bond but she is not allowed to enter the school premise or attend any event in the institute.

Her next court hearing will take place on May 30.