Things I described in above post,post above mention almost EXACTLY that.

Not only intrusion to privacy but quite complicated and would mean costs.

Let's say it not leaves the building. Ok. So you have to have server offline or it would be hacked. You have to record it on hard drives with some quality. Drives shall be probably encrypted too to avoid result of stealing it anyway (yes,some things can be stolen from schools). You have to monitor parent that not makes copy to take it outside (many risks). Sending data still must be done on cable,and you rather shouldn't use camera with wifi as wifi can be hacked quite easily (56bit is easy to break on modern laptop). Not to mention that school director ("boss" in current system) would get more power about teachers (how you can stop those person from using those recordings) what isn't already too good, as it is more centralization of power to those one person - such centralization isn't good.

Also there is problem I not mentioned about keeping it on school server. Such record can be deleted or edited sometimes. What makes recording useless.