By Waliur Rahman BBC News, Dhaka

Bangladesh pupils face toilet health hazards

Published in the capital, Dhaka, the study says in some cases, nearly 500 students share one school latrine.

The government says it is trying to improve the situation and that universal school sanitation will be achieved within the next five years.

The study surveyed nearly 4,500 schools across the country, officials said.

Lack of access to safe water and sanitation causes poor health, irregular school attendance and diminished performance Louis-Georges Arsenault Unicef

According to the Unicef study, Bangladesh averages one latrine to 152 pupils.

But in one of the worst cases, 479 students share only one school latrine. The study says the world average is 20 to 30 students per latrine.

'Kidney infection'

Unicef's chief of water and environmental sanitation, Paul Edwards, said the task of achieving the world average is huge as Bangladesh has nearly 80,000 primary schools and there are secondary schools to cover as well.

Experts say girls stay away from school for lack of toilet facilities

The researchers found no latrine in 6% of the schools, while 13% had non-functional latrines.

A leading child specialist, Salim Shakur, said the survey results were bad news.

He said sanitary conditions in schools deterred students from going to the toilet, leading in some cases to urinary and kidney infections.

Louis-Georges Arsenault, the country's Unicef representative, said access to water supply and sanitation facilities affect a child's ability to enrol and stay in school - especially for girls.

"Lack of access to safe water and sanitation causes poor health, irregular school attendance and diminished performance," he said.

Local government minister Abdul Mannan Bhuiyan, who is in charge of national sanitation coverage in Bangladesh, acknowledged that progress in school sanitation facilities needed to improve as a key factor for children's health.