A Year 4 boy was caught smoking and drinking during a school sports carnival, the Education Department has revealed.
The principal of a public primary school in the northern suburbs said the student had been suspended for smoking a cigarette and for sharing a "small quantity of alcohol" with two other students at the sports day last month.
The department said data on the number of suspension notices issued for substance abuse showed it was a "very rare" offence for Year 4 students, who would be aged 9 or 10.
It would not reveal how long the boy was suspended for.
The principal said the three students involved in the incident had been warned about the dangers of alcohol and smoking, counselled on how to make safe choices in the future and told to seek help from school staff if they were worried about any situations at school.
He said he had spoken to the parents of each of the students.
WA Primary Principals Association vice-president Ian Anderson said that type of incident was not common.
"It just highlights some of the challenges that schools have to face nowadays," he said.
Curtin University professor of health policy Mike Daube said though the incident was unusual, it was still worrying.
"We need to ensure alcohol and drug education are a well-supported part of every child's primary and secondary education," he said.
"It should be a mandatory part of the national curriculum."
School Drug Education and Road Aware manager Bruno Faletti said it was important for all schools to provide age-appropriate education programs on the dangers of smoking and alcohol.
But schools were in the best position to decide at what age to start the discussion about different substances.
"By Year 4 you would think most schools would have had some strong messages in their health curriculum about the harms from smoking," he said.
Primary school children would also examine the way alcohol use was promoted in society.
"Some schools would do an excellent job, other schools could do more," he said.