Thirty years ago, he failed the Primary School Leaving Examination (PSLE), but Ravindran Kanna is today a head teacher at the same primary school which once employed his father as an office boy.

To encourage children like the boy he once was, Kanna, 44, has written about his life and struggles in a memoir titled The Other Singapore Story, to be published at the end of this month by Marshall Cavendish.

The book tells of his impoverished childhood, how he nearly became a teenage gangster, but eventually turned around at a vocational institution.

He worked as a machinist and did odd jobs for years to pay for night classes at Clementi Town Secondary School, eventually completing his

O levels and doing an advanced diploma in industrial engineering and management at Ngee Ann Polytechnic before joining the Ministry of Education.

This year, he finished his master's in curriculum and teaching at the National Institute of Education, in line with the lifelong learner's award he received from then president S R Nathan in 2005.

Married to a fellow teacher he met at night classes, Kanna has two sons aged 13 and 10 and just shepherded the older one through the PSLE.

He laughs when asked what he would do in the event that either of them does not clear the examination. "The effort is important. If you put in the effort and you don't clear, it's okay. That's what I want to tell parents and children - that PSLE is not the only exam. There are other places you can go."

Though it will mean "you sacrifice your childhood" and the chance to have fun in secondary school, he warns.

When he failed the PSLE in 1984, his father Kanna Veerappan, not known to spare the rod, refused to beat him and only cried. Mr Veerappan worked several jobs at a time, from washing cars to working in a hotel laundry, and his greatest hope was that his three sons would do well at school.

Kanna wanted to do better after his failure, but fell into bad company at the then Ayer Rajah Vocational Institute. Luckily, a teacher's influence stopped him before he left for his first gang fight and a subsequent cash award for studying hard encouraged him to hit the books.

Today, at Bukit Panjang Primary School, he handles pastoral care and career guidance and tries to be a role model for his pupils.

Hoping to reach out to more young ones, he wrote his personal story and sent it to Marshall Cavendish in 2012. "Whether the book makes money is secondary," he says. "If the book can reach out to many students, then I've served my purpose.

"I want to let children know that all the kids out there are going through difficult times. You're not the only one."