Yin Guiling, who teaches English at a high school in Shenzhen, Guangdong province, said although the school has a busy schedule, some of her students still take tutoring courses during weekends in the hope of achieving high scores in the all-important national college entrance exam, or gaokao.

Many of the students who attend these courses paid little attention during school classes, and their scores have not improved much as a result of the additional studies, she said.

"If they do not want to learn at school, what makes their parents think they are willing to learn during tutoring courses?" Yin said.

Zhang Yu, vice-dean of Tsinghua University's Institute of Education, said the intense competition among students to take tutoring courses and learn ahead of the syllabus is not in line with the learning pattern for them and has had a serious adverse impact on the education system.

For example, when students learn mathematics that are too advanced for them, their brains are insufficiently mature for them to understand the underlying logic behind the knowledge, Zhang said in a China Central Television interview.

Instead, they have to rely on rote learning to remember answers. They also lose the opportunity to develop mathematical logic in learning new knowledge, she said.

Based on Zhang's research, students who have attended math tutoring courses in lower grades at primary school have slightly higher grades in the subject than their peers when they enter middle school.

However, in middle school, the former group improves more slowly than its peers, as the students have not developed the logic to learn new knowledge, she added.