Young Muslim boys read the Quran quietly to themselves, memorising each line as part of their religious education in a suburban school 40 minutes away from Kuala Lumpur.
Tucked in a residential neighbourhood in Selangor, Maahad Tahfiz An-Nabawi is among more than 900 new private Islamic schools that have mushroomed across Malaysia in the last six years.
Many Muslim parents see public schools as unable to build character, strengthen religious beliefs and instil good moral values in their children. So they are sending their children to these Islamic institutions, or tahfiz - the word literally means "memorising" (the Quran), - even though most of them charge tuition, while public schooling is free.
Senior clerk Zulkifli Ahmad is typical of Malaysians who think the switch is worth the cost. "Children who go to tahfiz schools are more polite, obedient and fulfil their religious obligations," he said, adding that he is less worried about his child coming into contact with bad influences in such a school.
Mr Muhammad Shariff Azhari, a director at Matan Centre, which runs three private religious schools nationwide including Maahad Tahfiz An-Nabawi, noted: "Society is returning to religion and there's a demand now for tahfiz schools."
Tahfiz education has become big news in Malaysia because of a tragic event in April - an administrator at one such school in Johor allegedly abused an 11-year-old boy so badly that he died. The case is under police investigation.
Also in April, Prime Minister Najib Razak gave RM30 million (S$9.7 million) to develop tahfiz education - a first by the government to provide financial aid to empower privately run institutions.
About the schools
Tahfiz schools were introduced in the 1960s when Malaysia's first prime minister, Tunku Abdul Rahman, started one in the national mosque in downtown Kuala Lumpur.
Many Islamic teachers - or ustaz - attribute the growth of tahfiz schools over the decades to Kelantan's state government, which is run by Parti Islam SeMalaysia. The party's revered former spiritual leader, Nik Aziz Nik Mat, affectionately called Tok Guru by his students, set up the state's first tahfiz school in 1992. With the state government's support, more than 100 tahfiz schools were set up.
As of January last year, more than 36,000 students were in 547 tahfiz schools registered with the state's religious department.
There is no known figure for enrolment in unregistered tahfiz schools nationwide.
The newly created Federation of National Associations of al-Quran Tahfiz Institutions told The Malay Mail Online there are about 1,200 tahfiz schools nationwide - 670 of them not registered with the state authorities.
Each school creates its own syllabus, with the central focus on memorising the Quran.
It is for the school to decide whether to offer classes for the high school certificate and help register students for the national examination.
A school also dictates its own annual calendar and fees.
However, tahfiz schools are not the only ones booming in Malaysia. Private educational institutions of all kinds are doing well, with international schools seeing a growth spurt, while enrolment at Chinese independent schools is also rising as more students ditch national schools.
But education at tahfiz schools is different from that at other private institutions. Each school sets its own syllabus, with an emphasis on memorising the Quran. So most students end up becoming ustaz after they graduate, contributing to a rising number of religious teachers.
Others pursue different courses in universities that are usually linked to Islam, such as becoming an imam or a syariah lawyer.
There are more than 600 unregistered tahfiz schools, and they are not subject to any one system at the moment. The result? The quality of tahfiz schools varies greatly.
"There are successful unregistered tahfiz schools with high fees and good management. Then there are the pondok (hut) school types that don't charge a fee and get volunteer teachers," said Mr Muhammad Shaiffudin Abu Bakar, the secretary of Matan Centre.
The government is aware of the need for integration and closer oversight, and is setting up a National Tahfiz Education Policy.
Although tahfiz schools have been urged to register with the government's Islamic department, Deputy Prime Minister Zahid Hamidi said the authorities would not force schools to do so.
"Registration isn't for enforcement. If they don't register, they won't receive help and students may not be able to pursue their tertiary education," said Datuk Seri Zahid earlier this month.
The Straits Times has found that many tahfiz schools do not provide a parallel system for students to sit the government-recognised high school certificate called SPM - a prerequisite for anyone seeking tertiary education in Malaysia and abroad. Some schools offer extra classes for SPM subjects but in cases where they do not, the responsibility falls to parents.
Clerk Nawi Jaiyas said: "I will have to look for private tuition for SPM when my son graduates from tahfiz school."
Still, the growth of Islamic schools has come amid rising concern worldwide that such schools could become hotbeds of militancy.
Lotfi Ariffin, an Islamic State in Iraq and Syria (ISIS) militant who was killed in Syria in 2014, was revealed to have jointly founded a madrasah in Malaysia's Kedah state, leading to fears that ISIS militants may influence students in some Islamic schools.
Last month, a religious school teacher in the state of Perak was arrested on suspicion of supporting ISIS militants.
However, a 2015 statement by the Home Ministry revealed that only 5 per cent of those arrested for terrorism links had religious school backgrounds.
Mr Shariff said people's perceptions of Muslims have been misguided due to ISIS.
"We don't talk about making bombs. That's not Islam. No religion talks about murdering people," he said, adding that "terrorism isn't defined by religion".
Still, a worrying issue is that the rapid speed at which such schools are being set up has left the quality of some lacking.
"Such schools without proper systems or administration exist. Classes get cancelled and there are no proper timetables," Mr Shaiffudin said. "But not all parents mind. It's a matter of choice. There are parents who are okay (with the situation) as long as their children get an Islamic education."