Education Secretary Christine Choi has called on schools to increase the number of mainland study tours they arrange, and not to limit the trips to older pupils.

Mainland tours are mandatory for students in senior secondary years as part of the new citizenship and social development subject, which has replaced liberal studies.

Choi told a Legislative Council panel on Friday that 497 schools have so far signed up for mainland trips offered by the Education Bureau and around 50,000 senior secondary school pupils are expected to participate in such study tours this academic year.

DAB lawmaker Starry Lee suggested that younger children should also be included in the programme, with Choi responding that schools should provide trips for pupils at various stages of their education.

"I agree that one study tour is not enough. We’ve encouraged schools to allow students from different grades to embark on trips to the mainland," Choi said.

"Schools can also launch themed projects, so their pupils can visit a location [on the mainland] to study a certain topic each year, so, after six years, these pupils would have a deeper understanding of these places in our nation."

Meanwhile, education sector lawmaker Chu Kwok-keung said being as many teachers are also required to join mainland tours, schools need more money to hire substitute staff.

Choi rejected this, however, saying schools should make sure they don't have too many of their teachers across the border at any one time.

She added that teachers who get promoted, as well as new hires, have three years to carry out their compulsory mainland trip, so schools have plenty of opportunity to make suitable arrangements.