A family has expressed their anger that a married teacher who had sex with their adopted eighth-grade son has been released from prison for time served.

Kathryn Camille Murray, 31, was in court in Harris County, Texas on Wednesday for her sentencing after she pleaded guilty to sexual assault of a child and improper relationship with a student.

But because she has been in jail since January 2013, the judge gave her credit for time served and ordered her to be released from jail without probation, KHOU11 reported.

As she left the court at the end of the hearing, she was seen smiling, KPRC footage shows.

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Freed: Kathryn Murray, 31, smiled as she was sentenced to time served on Wednesday for repeatedly having sex with her 15-year-old student - even after she was arrested and ordered to keep away from him

In court: She must now register as a sex offender and has lost her teaching license

'We are very disappointed with the sentence and never agreed with the sentence,' the boy's mother, Jenny Pallais, told KHOU. 'We are still working hard to put our family back together.'

Her son Jimmy, who revealed his identity to ABC's 20/20 last year, had been adopted by the family from Costa Rica and brought to the U.S. when he was 14 - and barely spoke any English.

Murray, who was 28 at the time, began tutoring the boy at Memorial Middle School to improve his English, and his parents noticed that he took a liking to the teacher.

'Every kid goes through that, has a crush on a teacher,' his father Alex told 20/20. 'This is an adolescent son with just a simple crush. That's it. We thought nothing of it.'

Arrested: Murray, pictured left in a school photo and right in a mug shot, was tutoring the teenager to help him improve his English and they began a relationship after he wrote her a note expressing her feelings

In court: Murray leaves a Houston courtroom with attorney Robert Ross in July 2012 after her first arrest

He wrote his teacher a note to tell her how he felt about her, but ripped it up and asked her to throw the pieces in the trash - but she kept them and put them back together.

'She said, 'I read your letter',' he told ABC. 'She told me, 'I really like you, like, for real.' I said, 'I really like you.' And she... told me, 'I know, but we can't have anything'.'

We are still working hard to put our family back together Jenny Pallais, victim's mother

The Pallaises expressed their concerns to the boy's principal and asked him to switch classes - but the teenager and teacher continued to speak on Facebook - and soon started a sexual affair.

They had sex in Murray's classroom at least twice, as well as at his home and even at a hotel after his father dropped him off at a school dance, according to reports.

Mrs Pallais then received a text message from the teacher that was meant for her son, reading: ''You know I love you... I don't know what we're going to do, but we're going to be happy together... I'm worried about how obvious we are at school. I miss you,' ABC reported.

Then her 12-year-old son told her that he had gone into his brother's room one day while his parents were out to look for the dog and found Jimmy and Murray in bed together.

Victim: Jimmy Pallais, pictured speaking with ABC 20/20 last year, was just 15 when he met Murray. After her arrest, he said that he felt guilty and depressed, and he considered committing suicide

Outrage: Jenny and Alex Pallais said they believe Murray took their son's childhood from him. Mrs Pallais learned about the affair after her 12-year-old son said he found Jimmy and Murray in bed together

His shocked mother went into her son's room and gathered up all the sheets and contacted the police, who ran a DNA test on the items.

'DNA from those sheets proved that she was there,' Alex Pallais told ABC.

Murray, who also had sex with the boy in her classroom, was arrested but released on $50,000 bail. She was fired from her job and ordered to keep away from the teenager.

But when he started sneaking out of his room at night, his parents hired an investigator who followed the boy to Murray's father's house.

Police arrived at the house and Jimmy, who was then 16, tried to escape through the back door. She was arrested again.

Scene: After learning about the relationship from her younger son, Mrs Pallais gathered all the sheets from her son's bed (pictured) and they later tested positive for Murray's DNA, she said

After she was arrested for the second time in January 2013, Jimmy said he became depressed over the guilt and considered committing suicide.

His parents said they feel the illicit relationship 'took his innocence away'.

'She robbed him of his childhood,' his father Alex Pallais said.

Murray will now have to register as a sex offender for life.

Her attorney Robert Ross said: 'I'm just glad it's behind us, so is she, so is her family. She'll start anew with a good life.'