A 13-year-old girl and a man and woman will face court after a teenage girl was allegedly punched unconscious outside a school in Wollongong.

Police allege the 15-year-old victim was punched in the head and stomach by a woman while being held by another teenager after school in the school carpark in Warrawong on Monday.

A 14-year-old boy who came to help the girl was also allegedly assaulted.

Police say the 15-year-old girl was then knocked unconscious when a man punched her in the face.

About 7.20pm (AEDT) yesterday police arrested a man, woman and girl who were taken to Lake Illawarra Police Station and charged with numerous offences.

The two adults, both aged 35, will appear at Port Kembla Local Court on 28 March.