Hong Kong pupils on Monday had mixed feelings about going back to school, with some happy to see their old friends again and others saying they wished the summer holiday was longer.

"I slept at around 9.30 last night because I was playing with my dad. [I miss the holiday] because I still want to play," said one pupil studying at a Tin Shui Wai school.

Another pupil said she was nervous because there would be many new faces in class.

Education Secretary Christine Choi wished pupils a good start to the academic year, and highlighted the need for mental health support.

Choi said as of July, more than 420 schools had signed up for the government's 4Rs Mental Health Charter.

The 4Rs stand for rest, relaxation, relationship and resilience, and the charter is designed to address the plight of students struggling with their mental well-being.

"I know some schools have their own mental health support programmes for students in progress or in future," she told reporters at a secondary school in Tuen Mun.

"I believe that as those plans are gradually integrated, more and more schools will participate in the 4Rs mental health charter, to encourage students to rest and relax, improve their resilience, and establish good interpersonal relationships."

Separately, the minister said her bureau has sent six advisory letters to follow up on a primary pupil who has reportedly been absent from school for more than two years.

Choi said the bureau hopes to help the pupil get back to school as soon as possible by getting in touch with different stakeholders.