A veteran educator herself, Mrs Marietta Koh pays around $2,000 per term to put her daughter through tuition classes.

This is despite her belief that tuition can hurt society, since not all can afford it.

Is tuition a necessary evil? She certainly thinks so.

Mrs Koh says: "The idea that education is the great equaliser used to be true, but things have changed as parents become more affluent.

"The rising trend of tuition is worrisome because it is money that gives parents the ability to purchase advantages for their children."

PHOTO ILLUSTRATION: ST FILE

Mrs Koh, once a secondary school and junior college teacher and later a tutor, knows of parents who pay $5,000 a month for tuition, as well as those who struggle to pay the fees.

Yet when it comes to her daughter, she admits that she has to think differently.

"When I think from a parent's perspective, my priority changes to what's best for my daughter. Every parent wants the best," says Mrs Koh, who is now a curriculum development consultant.

This compulsion to give one's children an academic advantage has contributed to a burgeoning industry that is worth more than $1 billion, up from $820 million in 2008.

Seven in 10 parents send their children to tuition classes, according to a 2015 survey.

Some, like Madam Mala Ramakrishnan, believe that tuition has become a necessity.

She took up a second job to pay the hefty tuition fees, believing the extra classes would put her children on par with others.

Brand-name tuition centres are also popping up in shopping malls islandwide.

There are around 850 tuition centres and enrichment centres registered with the Education Ministry, up from 800 in 2014 and about 700 in 2011.

So fierce is the competition that tuition centres have to innovate to stand out from the pack.

Centres differentiate themselves by offering additional perks, such as free shuttle services to the tuition centre and free ice cream while studying, reported The Straits Times last week.

MORE INTENSIVE

Mrs Koh says the more expensive tuition programmes offer a curriculum that is more intensive than what is taught in schools.

At The Learning Lab, where she used to give private tuition, primary school children even take up current affairs programmes so they can learn to be "more sophisticated" than their peers.

Mrs Koh says: "They learnt about current topics like the financial crisis in 2009, and are able to understand (news events) better. These children will have an edge over others.

Traditional tuition centres offer more exam-oriented tutoring to help students with their weaker subjects.

A former National Institute of Education lecturer, Dr Yeap Ban Har, says this trend of including play with learning is rooted in research and learning theories.

He says: "Maybe these tuition centre owners feel that schools are not doing enough of this and want to offer that experience for children.

"Plus, it offers parents who can afford it another option - not more of the same thing."

There are cheaper options, too, but experts say that parents are willing to pay more for a perceived guarantee that their children's grades will improve.

Dr Kelvin Seah, an economics lecturer at the National University of Singapore (NUS), says: "The effectiveness of tuition depends on the tutor and the way to know if the tutor is good or not is to see his past experience and record.

"That's why brand-name tutors, like some super tutors out there, can charge much higher rates."

Because those who can afford it will be able to pay for better tuition, Dr Seah believes that the obsession with tuition can end up widening the gap between "the haves and the have nots".

"It has been a focus of education research, whether tuition here leads to inequality and, by and large, research does show that it is the case," says Dr Seah.

While schools are perfectly able to help weaker students through supplementary classes, many parents would still rather pay for tuition.

Dr Seah says: "The reality is that parents think they are taking an educational risk here by relying solely on the school. They see other kids go for tuition, so their children have to go, too."

NUS sociologist Dr Tan Ern Ser agrees, describing tuition as an "inequality of opportunity".

Dr Tan says: "We have heard so much about parentocracy and how parents try to give their children an advantage in the mobility game.

"Tuition can un-level the playing field, giving students from families with the means a boost in their performance in academic subjects, exposure to enrichment courses, even grounding in useful skills.

"In short, it can result in unequal relative social mobility."