Computers in schools are failing to block inappropriate content, according to a new study.
Researchers from online safety company E-Safe Education say that ten per cent of harmful material can still be accessed in schools.
The companys managing director told BBC news: "We are seeing a new generation of multimedia content and images downloaded from mobile phones, pen drives and CDs and DVDs which do not always have words attached."
"Schools can be really surprised by what they see," he added.
The issue of child internet safety had been raised earlier this year on Safer Internet Day.
The February event was organised by international information network Insafe and focused on social networking sites.
Research released at the time by Microsoft showed that around a third of European teenagers had experienced online bullying.
Half of those surveyed said they use the internet without any parental supervision.