I used to work in the low-voltage systems (commercial paging and audio, security, video, fire alarm, etc.) insdustry and would talk to facility managers of school systems to help them with whatever it is they needed. On one visit to a medium-size central Indiana college town one day, the facility manager told me that the liberals in that town would NEVER allow video cameras to be placed in their schools, and view this as a violation of civil rights.
I have seen many schools that have cameras placed in the hallways and at entrances, card access systems for front door security, and all kinds of security that is supposed to keep people out, but I don't recall ever seeing a school with cameras in the classrooms.