As schools rush to embrace computer tablets as teaching tools, glitches have officials in a few districts rethinking the usefulness and even security of the latest technology trend.

The highest-profile snafu came in Los Angeles, where a $1 billion program—funded by voter-approved bonds—to provide Apple Inc. iPads for K-12 students came under fire after some students sidestepped the security system and accessed social media, online games and other content that was supposed to be blocked.

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