Rothwell was initially suspended with pay from the school, but since her guilty plea, she has surrendered her teacher's license and resigned from her position as assistant principal.
She was also given a suspended prison sentence of 10 to 21 months and is required to register as a sex offender for 30 years.
The mother of the 17-year-old victim spoke in court, saying her son's life has been turned upside down.
Sources said the sex acts with the 17-year-old happened three times in April and three times in July. Each time, there were two sex acts involved.
"I anticipate this working out very quickly, and that's the bottom line," defense attorney Trippe McKeny said.
The 17-year-old accuser was a student at the time.
Police acted fast in their investigation after hearing talk on campus between students, according to WSOC-TV.
"There was some chatter among students that was passed back and forth, which made its way to school administration," Gaston County police Capt. Bill Downey said.
Investigators said Rothwell began tutoring the victim last school year.
"Tutoring, the assistant principal, in this case, was helping the young man with some issues as far as school," Downey said.
Rothwell has over 10 years of experience with Gaston County Schools, according to the district’s website.
She is originally from Grand Rapids, Michigan, and taught exceptional children and English 9 and 10 at North Gaston High School.
She also taught at Springfield and Kiser elementary schools and Stanley Middle School.
Rothwell has been with Stuart W. Cramer High School since 2014. Her profile page on its website was taken down after she was booked into jail.
Police questioned the student and Rothwell, which is a process that can normally take months. The arrest came within a week.
"We don't make charges unless we know, and we have evidence (that) we can proceed to court with," Downey said.
Rothwell’s attorney said in court earlier this month what so many are saying at Stuart Cramer High.
"Everybody is shocked and completely flabbergasted," McKeny said.
Rothwell's husband and his family were in court to support her.
There was also a group of people at the courthouse to support Rothwell during her court hearings.
"She's got a kind heart," former student Jasmine Morgan said.
Morgan said she went through a troubled time and Rothwell counseled her and saved her life.
"If Ms. Rothwell hadn't been there for me when I was going through a lot of stuff, I probably wouldn't be here today," Morgan said.
The attorney claimed Rothwell helped so many students and that she worked with students with special needs for much of her career.
"Though these allegations are very serious, Your Honor, please, she has helped a lot of folks for a long time," McKeny said.