The challenges of replacing the Normal and Express streams with full subject-based banding should not be underestimated, Education Minister Ong Ye Kung said in Parliament on Tuesday.
His ministry will pilot full subject-based banding in about 25 secondary schools next year and progressively apply it to all schools, with streaming to end in 2024, he added.
He went on to explain: "Implementing full subject-based banding will be a multi-year transition.
"We should not underestimate the challenge of this move. There are major operational challenges, such as timetabling. Schools will need time to learn, adapt and innovate," he said during the debate on his ministry's budget.
For instance, Edgefield Secondary School - where each Secondary 1 class is made up of students from different streams - had to go through more than 100 permutations of the timetable before coming up with the final version.
In drawing it up, the school had to consider such factors as the availability of classrooms and teachers, and ensuring the students' school hours are not extended and teachers' workload not increased significantly.
Edgefield principal Lee Peck Ping also said in an earlier interview with The Straits Times that the school had tried to "allocate venues close to each other to minimise students' walking distance and to maximise curriculum time".
Mr Ong further explained in a video released by the Education Ministry on Tuesday that this latest change is "far more complicated" than the removal of the EM1, EM2 and EM3 streams in primary schools in 2008.
"What we are doing today for secondary schools is informed by (that) experience... We are doing a similar effort now, but it is far more complicated because there are many more subjects," he said.
"We introduced subject-based banding (in secondary schools) as a pilot in 2014. In 2018, we extended it across the system.
"Today, in 2019, we will take further steps that will eventually - by 2024 - merge all three streams into one course. And within each course, (there will be) many subject bands."