An email containing graphic content has been sent to students at an Auckland high school - on their school accounts

Parents of Rosehill College students received a message warning of the disturbing email - sent from an external source.

It's been removed from all student accounts and the ability for outside agencies to contact students has been turned off.

Secondary Principals' Association President Vaughan Couillault says the school's response indicates it was serious.

He says it feels like a nasty one off event.