She is shown to teach ICT, as shown in New Term, Points, and Sick where she is teaching ICT. She is overweight, as pointed out by Josh and Owen.
Her first appearance is in Back to School where Nathan introduces himself to her in the staff room, however he does not fancy her and was only trying to be friendly. She is not very popular amongst the pupils and can get quite shouty.
In Series 2 she is made deputy head by new headteacher Mr Bell and frequently goes along with his schemes including attempting to sell half of the school off to developers and kick the 4OCC into Fowlmere. However, she ends up agreeing to put Project Zenith on hold after the news company were called to broadcast the protest.
In Series 3 she only appears in the first two episodes as a main character, in Merger it is revealed she has went to teach at the private school Ryan and Molly attend. In Audition, after a student panel (accidentally including some 4OCC members) interview Mr Bell and Mrs O'Brien to see who should become the head of Elmsmere, O'Brien is sacked, Bell is demoted to a teacher, and Andress becomes head of Elmsmere.
In Series 4 she is shown to be a strict and unsupportive head who frequently argues with rebellious pupil Clem Burton. She is also shown to undermine Mr Bell despite their good relationship in Series 2, for some reason she has grown to dislike him. Mr Bell is angry about his demotion so he anonymously sprays insults of Andress around the school.
In Series 5 it is confirmed Anita Andress has left Elmsmere, with Helena Goodman taking her place as headteacher.