Schools worldwide have helped to fuel a boom in the market for tablet computers, with the number of the devices in American and British classrooms doubling in the past year. Other countries, such as Turkey, Singapore and India, have also pledged to give each child access to a tablet.

But large-scale programmes in the US, costing hundreds of millions of dollars, have had to be halted after problems including security breaches and hardware failures.

The most embarrassing involves the Los Angeles Unified School District, the second biggest school district in the US, which signed a deal worth $500 million (#163;313 million) with Apple to supply each of its students with an iPad.

But just weeks into the new term, city officials are holding crisis meetings after students hacked the tablets, enabling them to access restricted websites and download games. Last month, more than 300 students at Roosevelt High School managed to circumvent security on the iPads, allowing them to surf and download non-approved content.

The district has prevented students from taking their devices home because of concern among parents that they will be forced to foot the bill if the computers are lost or damaged.

The problems have led the school board to announce that it will be reviewing the programme at the end of the month. Monica Ratliff, who chairs a committee overseeing technology in the district, called for the review and admitted to errors. “Clearly, the board and the district should have answers to the many questions that have arisen,” Ms Ratliff told the Los Angeles Times.

Other parts of the US have experienced similar issues, particularly North Carolina, where the Guilford County Schools district signed a deal for 15,000 Amplify tablets in a contract worth around $30 million (#163;19 million).

Amplify is the latest technology enterprise to be started by media mogul Rupert Murdoch. It aims to provide schools across the US with personal tablets for their students, pre-loaded with curricula and other educational content.

However, Guilford district officials decided to suspend the programme after 10 per cent of the computers were returned because of broken screens, 2,000 students reported problems with the cases and others handed back their devices after their chargers melted. Guilford’s superintendent, Maurice Green, said the problems were “extremely disappointing”.

Amplify said it had advised the district to stop using the chargers and that it was working with staff to solve the problems. “Out of an abundance of caution, we proactively asked Guilford and all Amplify tablet users across the country to stop using the ASUS charger until we could determine what caused it to melt,” a spokesman said. “Nothing comes before the safety of our students, teachers and their families.”

The number of breakages in Guilford County was “much higher” than in other areas of the country, the spokesman added.

In Texas, meanwhile, the Fort Bend Independent School District decided to scrap its tablet programme last month - a review found that it had “fallen short of its mission” after only 19 months. The iAchieve initiative included giving 6,300 iPads to students to deliver interactive science curricula, at a cost of $16 million (#163;10 million).

“The review was not positive,” a statement from the school board said. “Auditors noted several findings in their report that will need to be explored including unrealistic goals, poor contract management practices and poor project management.”

Miles Berry, board member of UK ICT subject association Naace and principal lecturer in computing education at the University of Roehampton, said the incidents ought to act as a warning for anyone planning to distribute tablets in the UK.

“This should suggest a degree of caution in the rush to implement 1:1 tablet deployment. Schools should think carefully about how they want tablets to be used, and how their pupils might want to use tablets. If it’s merely to provide locked-down access to pre-packaged curriculum content, there may well be easier, cheaper and more robust ways of doing this,” he said.