A 15-year-old girl denied stabbing 14-year-old classmate when she appeared at Luton Crown Court on Monday.
The teenager, who was 14 at the time of the alleged offence, pleaded not guilty to a charge of wounding with intent to cause serious harm on 15 July.
It is alleged she attacked the girl during morning break at the Thomas Alleyne School in Stevenage, Herts.
Her trial, which is expected to last three weeks, is due to take place in March next year.
The girl, who cannot be named for legal reasons, was remanded on bail with stringent conditions until the next hearing.