The pair, who have pleaded guilty to one count each of affray over the February 20 altercation, attacked the young girl in the car park at Warrawong High School, leaving the teen in need of hospital treatment.

During the fight, the woman repeatedly punched the teen in the head and stomach, until she fell to the ground.

The woman then punched a 14-year-old boy, splitting his lip, as he came to the girl's defence.

Her de facto husband, who had been watching initially, then grabbed the teen by the hair as she struggled to her knees, shaking her so violently she fell back to the ground and soon lost consciousness. The semi-conscious teen was taken to Wollongong Hospital suffering a concussion, as well as swelling and bruising to her head and side.

On Monday, Wollongong Local Court heard the couple had been involved in a heated confrontation with office staff earlier that day, threatening to "take matters into their own hands" if the school did not act on their daughter being bullied.

Less than four hours later, the Warrawong couple attacked the two children.

Yesterday, the man, who initially pleaded not guilty to assaulting a school student while attending school, common assault and affray, pleaded guilty to the affray charge.

The other two charges were withdrawn.

Setting a date for sentencing yesterday, Magistrate Les Mabbutt noted the gravity of the offences.

"I view these charges very seriously, because of both where they took place and on whom," he said.

"Children at school should be protected."

The pair will be sentenced on February 4 next year.