It is common for pupils' results to dip in upper primary school as they adjust to more subjects and tougher content - and parents need to readjust their expectations.

The introduction of science as the fourth subject at Primary 3 is one factor, but the increasing complexity of concepts being taught also adds to the dip, said educators, who urged parents not to be unduly alarmed. Pupils tend to improve after some practice.

Madam Joyce Ong, 42, said her daughter, now in Secondary 1, had experienced a dip of around 10 marks in mathematics and science when she started Primary 4 and 5.

"As new and more complex topics are added, children might fumble a bit," said the property agent.

But extra coaching, sometimes through tuition, helped her daugher to catch up, she added.

"Some of the problem sums can be quite daunting... I was also unsure which methods to use, so I can imagine it was more difficult for an 11- or 12-year-old."

However, large drops in scores could point to more serious issues. In the recent coroner's report into the death of a Primary 5 pupil, it was stated that he had scored 20.5 out of 100 for mathematics and 12 marks for his Higher Chinese exam. For his English language, Chinese language and science papers, he had 50, 53.8 and 57.5 marks respectively.

His principal had testified that the boy had been an "average" student since he started school, and in previous years, had obtained an average of 70 marks for his subjects.

Experts said the huge drop may have meant that the boy was coping with other issues as well.

Several parents also questioned if he should have been allowed to take Higher Chinese as he was an "average" student.

A 51-year-old former primary school teacher said that pupils are given the choice of taking up Higher Chinese at the end of Primary 4 if they do well in the examinations for their languages.

"Schools will also hold briefings after the exams at the end of the year to explain to parents their selection criteria - usually 75 marks and above," he said.

"Higher Mother Tongue is an optional subject and if, in Primary 5, the pupil fails or is unable to cope, parents can still write in to ask that he or she drops the subject.

"Parents typically like their kids to take a higher language because it looks good on their portfolio.

"But it doesn't seem very wise for them to continue taking the subject if they don't do well, even if they qualified for it earlier."