All PTAs have the right to develop their own policies and procedures as do any parent group unless there is a resolution or position that says it cannot be done but these policies and positions are supposed to be brought to the membership for implementation.
Like pals, there could be an issue of liability here (if for some reason the school does not cover the safety of a volunteer, the PTA insurance would) Or it could be that the PTA is enforcing the privacy of your own information by implementing the volunteer. Is that the case? I have signed confidentiality agreements etc, as a PTA President.
The first step would be to ask the PTA "why they are doing this?" Is there a history that you are unaware of? Does the school request this or is it just a PTA policy? (I find it hard to believe that a decision like this was made without school input)
IMHO, this is something the PTA board members should do, if they should be doing it at all
Not really, it's something that the school should be doing because it's their job. Since they aren't doing their job and they are relying on volunteers to do it, then if your school has 500 students- 4 people would have to call 500 parents (if the board had to do it and as a board member, I don't have the time to make 500 phone calls), or 1 or more parents from each class would have to call 23 people. It's most efficient to delegate it to as many people as possible. Hence the old fashioned phone trees.
(I don't like the fact that my telephone number is floating out there on some list).
Unless every parent in the classroom is a member of the PTA, then it's the school that is putting your phone number on a list unless they only call PTA members which I doubt.
If this is a school policy or school approved PTA policy (again if the school didn't back it up, it would be near impossible for the PTA to enforce) then you can fight to change it (follow the channels of command- site based administration- area superintendent etc) or if it's important enough to you and your reasons for not joining the PTA aren't based on strong personal convictions (is that the reason you won't join?) then just join or you can just let it go. If it is strictly your school's PTA position (and again, highly doubt the school isn't involved here)then join your PTA and work to change the position. Those are basically your options.