Magistrate David Williams accepted a medical certificate for the teenager's absence in Nowra Children's Court on Thursday, February 20.

The teenager from Airds in south-west Sydney faces a charge of intentionally causing fire and being reckless to its spread.

The charges stem from an incident on January 30, when grass near the Princes Highway at Falls Creek, south of Nowra was allegedly deliberately set alight.

Police allege the teenager was staying at a nearby property and was seen by witnesses fanning the grass in the paddock on the western side of the highway between Forest and Parma roads around 3.30pm.

Police have been told white smoke was seen and moments later several flames erupted in the grass.

The fire was extinguished by members of the public.

Magistrate Williams directed the boy must attend his next court date in March.

Until then the teenager remains on strict bail, including having to live at home and having to be in the company of either of his parents at all times, other than when at school.

He can be in the company of a responsible guardian with the written permission of either parent but that responsible guardian must be in possession of the letter at all times when in the boy's company.

He is also not to be in possession of any fire ignition devices.

Read more: Crime/Court