In the past three years, so many students have started choosing science subjects for their HSC that Kirrawee High School has run out of laboratories.

The school, in Sydney's south, is going to start bringing in "portable trolleys", or mobile science labs, so that students in regular classrooms can keep doing experiments, head teacher of science Brett McKay said.

Kirrawee High School head teacher of science Brett McKay is this year's winner of the Prime Minister's prize for excellence in science teaching in secondary schools. Credit:Brook Mitchell

About 60 per cent of Kirrawee High's year 12 students are about to sit at least one HSC science exam, and a slightly higher proportion of year 11 students are studying one or more science subjects, Mr McKay said.

However, the real surprise came when year 10 students recently made their HSC subject choices.