An 18-year-old man has been arrested on suspicion of murdering Leonne Weeks, 16, who was found dead on a path in Rotherham.
CCTV Cameras In London Schools
More than 200 schools, including 25 in London, are using CCTV cameras in toilets or changing rooms.
The figures have been published under a freedom of information request by Big Brother Watch.
There are now more than 100,000 CCTV cameras in secondary schools and academies across the UK.
The campaign group believes the research raises serious questions about the privacy of schoolchildren.
A Department for Education spokesman said: "We have already acted to make it unlawful for schools to use biometric data like fingerprints without parents' permission.
"CCTV can be beneficial in some cases but this is a decision that head teachers should take.
"Schools using CCTV are required by law to adhere to the Data Protection Act."
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A man has been fined £1,800 for flying drones over Parliament, near Buckingham Palace and over football stadiums.
Government to investigate after some restaurants accused of withholding tips
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