Activation Screen permanent bypass?? Various phones

I am working on a project for a school system where they want to used deactivated donated phones in the classroom for WiFi access only.
They will be reset to Factory Defaults, so we'll need to get pass the Activation screen.
It will be a variety of phones so that is why I am posting this here.
It appears there are several different ways of bypassing the screen.
I seriously doubt that they will allow Rooting of the phone, but I will pass it along as a suggestion.

Seems like the most common is the 4 corner clockwise tap. This seems to work for HTC and Motorola.
What I cannot find is if this is permanent or not? If the phone Is powered off and then back on, does this have to be done again or is it once and done?
I've read both, but without device in hand, I cannot confirm or deny.
Is there a list out there for all the models that support this?

Samsung looks like you have to dial *#83786633
But this does not seem like a permanent solution--has to be done every time.
Permanent seems to Root and delete or freeze phone.apk or setupwizard.apk??

Thanks for any help on this endeavor!! It will be appreciated.