Pakistan has about 17,000 religious schools, or madrassas, which provide children with free religious education.
This means they have to memorise the Koran from as young as five-years-old.
There are nearly 2m students enrolled in Paksitan's madrassas.
But a 9/11 commission report in the US dubbed them as as "incubators for violent extremism".
BBC Urdu's Asif Farooq explains the increase in their popularity.
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