The names, addresses and personal information of pupils may have been accessed by criminals during a "significant cyber-attack" during half term, a school has said. 

The Billericay School, in School Lane, has re-opened today after the cyber-attack, which left teachers and staff locked out the system, forced the school to remain shut yesterday. 

Headteacher, Patrick Berry, wrote to parents yesterday to update them on the situation and revealed "name, address, basic medical notes, date of birth as well as contact details for parents and carers" could have been accessed during the attacl. 

He added the school "cannot be sure what specific data has been accessed or exported".

A police investigation is also underway, according to the school. 

Mr Berry said: "We are working with Action Fraud, a branch of the Police to investigate this attack but please be vigilant when opening emails and webpages to avoid criminals harvesting user credentials via any email addresses we may hold for you.

"We would suggest that you take preventative action such as changing personal passwords.

"We sincerely apologise that this potential risk to your personal data may have arisen and are doing all we can to strengthen our defences against cyber-crime."

All parents have returned to school as normal today, with the school still addressing "ongoing digital challenges."

The school has also recommended students bring a packed lunch today and tomorrow as the school is facing issues their cashless payment system.