'I used to work in schools, where I was on the school staff'. Sic et simpliciter.

I like Grammaticaitaliana's variant. Although, a case could be made that what you already have is technically correct, so the minimum change to make it correct would be no change. :) However, the intent of the sentence feels to me like "I have worked on the staff of several schools."

Hi, I am sorry, but your question is not clear. I assume that you wanted to say as follows: 1. I used to work in a school as a school staff 2. I have worked in many schools as a school staff 3. As one of the school staff, I also used to do my day to day activities. There may be many more meanings. Please choose which suite your intent. Thank you om