After reading so many gripes about IT teaching staff with very little idea about the subject, I thought my experrience in my second year of teaching might be of some interest.
I went into teaching (as a Maths teacher) after about ten years as an analyst/programmer (this was in the late 70s so that was an impressive amount of IT experience)
After I had been teaching for about 2 years, the school decided to to begin teaching what was then called Computer Studies, and an advert appeared on the staff-room nocticeboard offering promotion to anyone able to take responsibility for that. Naturally I applied.
The job was given to a colleague who had become first become interested in computers when the advert went up, because (I was told) she had been "keen enough to prepare for the interview by reading up about the subject"
Reading one book sometime during that week made her more qualified to teach about computers than I was, apparently.
(Note: at that time I could have WRITTEN a more advanced book on the subject than the one she read.)