An unencrypted memory stick and has been missing since July 1 , 2011 when the device was left in a laptop at the councils offices by a special educational needs teacher . When the teacher returned to the laptop the memory stick was gone and it has never been recovered . The device contained sensitive personal information about the 286 children who attended local schools , including information about their mental and physical health problems and teaching requirements . The device also included the pupils dates of birth and some included details of their home addresses and information about their home life . ;