ISLAMABAD, : Two young boys kneel over small white tables, intently studying the Koran at a madrassa in Pakistan.

The Al-Nadwa Madrassa in the hill station of Murree, 30 kilometres (19 miles) from the capital, Islamabad, is part of an established alternative system of education in the South Asian nation.

Private schools, charitable institutions and religious seminaries are stepping in to supplement government-run schools to help meet the education needs of an estimated 50 million school-age children.

Despite 220,000 schools nationwide, more than 20 million children are not in school, the government said in a 2016 report.

The government has pumped money into schooling, with the education budget swelling by 15 percent every year since 2010, according to education consultancy Alif Ailaan.

The United Nations estimates Pakistan's current education budget at 2.65 percent of GDP, roughly $8 billion, or around $150 per student.

Private educators say the country's education problems are not only due to a lack of funds but also inadequate teaching.

"It's not the number of schools, it's the quality, the attitude," said Zeba Hussain, founder of the Mashal Schools which teaches children displaced by war in the country's north.

Hussain started the charitable Mashal Schools after she met a group of refugee children while visiting the hill areas surrounding Islamabad.

Federal education director Tariq Masood said blaming teachers was unfair. He said population growth and funding were the biggest challenges faced by government schools.

Masood said government schools adhered to a nationwide curriculum that was being constantly reworked and improved.

"No one who is underqualified can enter the government system. There are fewer checks in the private system," he said.

The country's poor often send their children to one of the thousands of religious madrassas (the Arabic word for school) where students live and receive Islamic instruction.

Most operate without government oversight and some madrassas have been criticized for their hardline teachings of Islam.

The madrassas say they provide shelter, three full meals, and a good education to young people whose families are unable to make ends meet.

"In certain cases people send their kids because they can't even afford to feed them," said Irfan Sher from the Al-Nadwa Madrassa.

He said Pakistan's future hinged on education for its youth.

"The overall policy should be changed...they should understand that if they want to change the country the only way is to spread quality education,"-Reuters