About 700 secondary school teachers are expected to join the next round of a voluntary retirement scheme as pupil numbers shrink.
The Education Bureau will seek funding from the Legislative Council in the coming weeks to finance the scheme, although officials have not revealed how much it will cost.
Because of a drop in the birth rate 12 years ago, the next intake for secondary schools is expected to drop by 5,000 and to drop further until 2017, when a rebound is foreseen. By that time, secondary schools' annual intake will be down by 11,000, officials say.
School principals and others say the government should seize the opportunity to implement small-class teaching.
The bureau discounted the sustainability of such a move.
"This is just a temporary issue," a bureau spokeswoman said. "[By implementing small-class education], does it mean we will have to add more schools in future? As we are aware, finding land has been difficult. Putting up a school takes six to seven years."
The spokeswoman said the bureau's goals were to prevent schools from closing due to shrinking intakes and maintain teaching manpower to cater for a future increase in population.
The bureau said eight out of more than 400 secondary schools had closed since 2006 because of falling numbers.
Last year, 200 popular secondary schools agreed to cut by one the number of Form One classes in order to divert pupils to other schools.
Legislator Ip Kin-yuen, of the education sector, said the government should grasp the "golden opportunity" to have smaller classes.
As government grants to schools are determined by the number of classes they run, a reduction would further strain resources and increase teacher workload, Ip said.
"[Cutting classes] cannot solve the problems of schools," said Ip, who is collecting signatures from lawmakers to press the government to back smaller classes. It will be discussed in a special meeting of Legco's education panel on Friday.
In 2005, the education authorities sought HK$500 million to embark on the first round of the voluntary retirement scheme. By September last year, 758 secondary school teachers had signed up. The bureau will
seek funding to continue it until 2017. Teachers under 60 with more than 10 years' experience can apply.