Children are at a risk of being groomed for sexual abuse because some schools are failing to adequately protect them from online harms, experts say.
Research from 14,000 schools identified a "troubling" suggestion lessons had not been learned in parts of England that saw child exploitation scandals.
Rotherham, Oldham and Hillingdon were among the worst performing areas.
The Department for Education and Rotherham Council have been contacted for a response.
The research was completed for the UK Safer Internet Centre.
Schools involved in the research were asked to provide details of measures taken to protect children, such as internet monitoring, content filters and training for staff.
UK Safer Internet Centre director David Wright said: "At a time where children are relying more and more on the internet for learning, entertainment, consumption and socialising, we see some schools desperately need to up their game when it comes to making sure children are safe online.
"This troubling data indicates some serious lessons are just not being learned in key areas of England where we know children have been sexually abused and exploited.
"Online safety should always be considered a priority. If children are not kept safe and aren't taught about the potential risks of being online, they could be left vulnerable to exploitation or abuse."