[senco-forum] CCTV?

Having voiced my concerns to my Head,  about working alone with children 
in an isolated room, his suggestion was CCTV!
I'm not sure...Does anyone have experience of this in their 
classroom/office(my room is used for both) We already have cctv in 
school for entrances etc.
Are their confidentiality implications? with no sound would it provide 
evidence any way?
Kate