The average teen drug user takes drugs for the first time at 15, according to the Security Bureau's Narcotics Division.
Students make up 26 per cent of drug users under 21, Commissioner for Narcotics Sally Wong Pik-yee said yesterday.
Recent cases of drug use in schools have aroused public concern, but the government will not speed up the implementation of voluntary drug tests in schools.
It will roll out a pilot scheme for such tests next year, as planned. The scheme could be extended to all primary and secondary schools in 2011, Ms Wong said.
A public consultation by the police will take place in the fourth quarter.
'We expect reported cases of teenage drug abuse to rise in the short run,' she said.
Extensive reporting on pop singers Jill Vidal and Kelvin Kwan Chor-yiu, arrested for possessing cannabis in Tokyo, has raised public awareness.
Ms Wong said she 'did not exclude the possibility' that some schools hide drug-abuse cases to maintain their reputations, but more schools had been taking the initiative recently to provide anti-drug education in co-operation with NGOs.
To identify students who may be at a higher risk, the division sent 27 extra communication officers to schools this year. Two-day training sessions were provided for social workers and teachers.