In October, Education Queensland banned all state school teachers from using sites such as Facebook to communicate with past and present pupils.

Victorian teachers are not expressively forbidden from such contact.

A Department of Education and Early Childhood Development spokeswoman said the department did not dictate what kind of technology a teacher used outside school hours but it did require that any interaction with students was on a strictly professional basis.

"It's common for schools to have Facebook groups, which are created by former students wanting to stay in touch."

But an outer east secondary school principal said most schools banned access to Facebook through their internet networks. Michael McNamara, principal at Croydon Secondary College, said the school did not use Facebook, Twitter or MySpace to engage with its students, but did teach and reinforce "the dangers of cyberbullying".

He said the school was not involved in managing two Facebook accounts for Croydon Secondary College, which have more than 1000 members between them and where past and present students can share memories and information.

While many such sites are used to get in touch with long-lost friends, Mr McNamara said the school relied on more traditional means to contact past students.

He said teachers using social networking sites were bound by the Education Department's Code of Conduct, which states that a "professional relationship will be violated if a teacher ...holds conversations of a personal nature, or has contact with a student via written or electronic means including email, letters, telephone, text messages or chat lines, without a valid context".