Five WA students have been suspended over the past year for dangerous, destructive and offensive behaviour on school buses.
The offences relate to fighting, interfering with emergency equipment and destroying property.
They all occurred on the free "orange" school bus service that is provided in regional areas - and for special needs students - by hundreds of individual contractors. More than 26,000 students use this service every school day.
"While we ask that all behavioural issues on our orange school buses be reported to the Public Transport Authority, in many cases low-end offences are handled locally between the contractor, parents and school," spokesman David Hynes said.
"Of the 30 behavioural issues reported to the PTA in 2011-12, nearly all were at the lower end of the scale - failure to wear a seat belt, distracting the driver with persistent noise and swearing."
But five incidents were considered serious and led to the short-term school suspensions.
Ray Gannaway, the chairman of BusWA, the body that represents orange bus drivers, said the orange bus service was the best system for transporting students in Australia.
"A relationship develops between the driver, the students and the parents that provides the mechanism to manage any incidents that might arise," he said.
Mr Gannaway, who has been driving buses for more than 20 years, said older students were often appointed as bus monitors or prefects to assist younger children and help control misbehaviour.
In addition to the "orange" bus service, more than 25,000 students in Perth and larger regional centres pay a 50¢ fare each day to use a regular bus service or, in some cases, additional services for specific school routes.
A search of incident reports provided by bus drivers to the PTA in 2011-12 found 108 that referred specifically to student behaviour. Mr Hynes said most of these incidents related to swearing, graffiti, littering and assault and when an offending student or groups of students could be identified, the school principal was advised.