Jasmine Thoi, 14, has tuition outside school for her two strongest subjects, Chinese and Maths - even though she already gets As in them.
The East Spring Secondary student is among a rising number of youngsters who are opting for tuition, regardless of how good their scores may be. She said: "Tuition lets me explore more and learn faster than my friends."
Even students at tertiary level are getting in on the act.
Ms Vivian Koh, 20, a first-year social sciences student at the Singapore Management University, will start tuition this week for a calculus module.
"We're learning so fast in university," she said. "I'm not good in maths so I'm lost in class."
A week ago, Senior Minister of State for Education Indranee Rajah told Parliament that tuition for children who do well is counterproductive.
But tuition is not just for the weak and struggling. Many straight-A students are seeking help so they can maintain their standards or do even better.
Recognising this, tuition providers like GrayMatter Education Centre cater to students including those in the Integrated Programme, which takes in the top 10 per cent of each PSLE cohort.
Twelve-year-old Christie Ko is another high-performing student who has tuition, studying Chinese, Maths and English. The Primary 6 pupil in a girls' mission school, who gets As for all her subjects, said: "If I don't work hard, my grades will fall. Tuition helps to maintain my grades and ensure I do my work properly.
"My tutors teach ahead, so I understand faster when my school teacher starts a new topic."
A mother who declined to be named said her daughter, a Primary 6 pupil at Raffles Girls' Primary, has tuition in all subjects so her grades - consistent As - do not slip. "Tuition is a form of revision for her, to reinforce concepts, and tackle questions not covered in school," said the housewife.
Latest figures from 2008 show Singapore households spent about $820 million on private tuition, up from $470 million in 1998.
It is a growing business. There are 800 tuition and enrichment centres registered with the Ministry of Education, up from about 700 last year and 500 in 2010.
Mrs Amy Bellars, who owns Growan Learning Centre, said: "These kids' basics are already there so when they come to us, they are looking for teachers who can give them that extra edge.
"I have a pupil who is No. 1 in his primary school but he feels he needs tuition because he's afraid he'll drop to No. 2."
Mrs Summer Toh, 32, who set up The Water Family Enrichment Centre, sees a mix of strong and weak students. For stronger ones, "90 marks is never enough, and even if they get full marks, they want to maintain it," she said.
Centres like Maths Hub also cater to "specialised" needs, like preparing students for maths and science competitions.
Undergraduate students like Ms Koh form about half of private tutor Ng E-Jay's pool of students.
Mr Ng, 36, who teaches maths, physics and chemistry, said: "At this level, it gets more complicated. Some need help in explaining difficult concepts."
But demand for tuition from genuinely struggling students has not lessened either, said True Learning Centre owner Max Tan.
Managing director of Adam Khoo Learning Centre Frederick Tan said most of his students are not doing very well, but some are already riding high.
"The message from them and their parents is very clear," he said. "They want to learn beyond what schools are teaching, like more problem-solving methods."