"I felt it had imposed great pressure on our life and the relationship between me and him was very bad," recalls Cheung, 51. "Sometimes he screamed [over homework]. Sometimes I screamed. Sometimes we both screamed."

Cheung is not alone. Official figures show there were 36,190 pupils with special educational needs in mainstream primary and secondary schools across the city in the last school year. Cheung says teachers have been pressurised to give pupils increasingly heavy homework and drilling due to the focus on raising TSA scores, and these children's needs for special attention and diversified teaching methods are often ignored in such a high-pressure environment.

The exams were introduced in 2004 to track the development of Primary Three, Primary Six and Form Three pupils' basic knowledge in Chinese, English and mathematics. But parents, teachers and schools have increasingly criticised the exams for leading to excessive drilling and homework, and called for the exams to be scrapped in Primary Three.

Some school supervisors, including Legislative Council chairman Jasper Tsang Yok-sing, say their schools were pressurised by the Education Bureau to raise TSA scores, although officials say the exam results will not affect secondary school allocation or the distribution of resources to government-funded schools.

"TSA has turned schools into places not pursuing knowledge but scores," says Cheung. "This not only has affected common children, but also marginalised children with special educational needs. I only hope [the authorities] can cancel TSA and give more space to schools."

This was why Cheung and a group of other parents founded Sen Rights in 2013 after a trip to Taiwan, where they visited universities and parent groups and learned it was possible to create a happy and caring learning environment for special-needs children in mainstream schools. They also found out in the same year, from a series of 10 Legco public hearings on special-needs education where hundreds of parents spoke, that many more parents were in a similar plight if not worse. The group aims to pursue better-quality, more diversified education for children with special needs in mainstream schools.

Cheung gave up her work as a building designer two years after her son was diagnosed with autism in 2007 at the age of four. She first sent him to a mainstream primary school in Sha Tin that upheld the philosophy of "high motivation study" through activities and exploring instead of score-oriented learning.

She says her son was happy in the first two years because his teachers had the time and space to tend to his needs. Once, she recalls, a teacher tried to persuade him not to jump down stairs. But being stubborn, a typical characteristic of autistic people, he refused to listen and even hit the teacher in a fit. But the teacher was persistent and offered to accompany the boy to walk up and down the stairs twice. The boy eventually gave in, to Cheung's surprise.

But when her son entered Primary Three in 2011, a new principal with an opposite teaching philosophy took over. Cheung, who was in the parent-teacher association at that time, remembers the principal telling her and other parents that the school's TSA results had been below average.

Several long-serving teachers left the school due to the clashing philosophy and Cheung took this as a warning sign of a looming change to more spoon-feeding, memorising and school work. She soon transferred the boy to another mainstream primary school in the same district.

But things got worse, as that school had an even longer tradition of heavy work. On several occasions the boy rushed out of the classroom in despair at his studies.

All this was driving Cheung to the limit as she had already been occupied with handling her son's sudden outbursts in daily life and coaching him in simple life skills that he found difficult to acquire, such as how to tie his shoe laces. The school was not helping her but making things worse.

After only half a year in the second school, Cheung transferred the boy again to a school for children with autism in Hung Hom.

She feels that the government - which has been promoting an "integrated education", where children with special needs can enjoy quality education in mainstream schools - is actually pushing these children out of the system by putting them under the pressure to achieve higher scores.

Although people like Cheung have been trying to stop the TSA for years, she believes that recent large-scale protests by parents show the situation has reaching a turning point.

"Now drilling has started as early as kindergarten," she says. "It's like a bottle of water. When we were shouting 'it's going to spill', nobody listened. Now it's spilled."

Josephine Cheung Man-sen

Graduates university and starts work as a building designer

Gives birth to her son

Son diagnosed with autism

Quits her full-time job as an architect

Transfers son to Aoi Pui School in Hung Hom from a mainstream school in Sha Tin

Visits Taiwan with a group of other parents

Attends public hearings in the Legislative Council on special education

Co-founds Sen Rights

Attends Legco public hearing on the Territory-wide System Assessment