Printer to all User wont work

[HCSCTECH]

Hello, I am a tech and I work for a high school. For the last 2 weeks me and 2 other tech's have worked on this same problem and tried every thing we could think of and have still came up short. We need ALL users to be able to print to one printer when we set it up on ONE account. Well we figured out how to make new users who log on to the machine have it set as their default printer BUT (the problem we are having) is we need all users who already have a local user account on the machine to have it set as their default printer as well. So the problem in a nut shell:

New users logging onto the machine for the first time will have the printer we want set as their network printer and it will be their default. Thats fine.

HOWEVER, When some one who has already logged on before and it has already made their local user profile, their printer is whatever they set as the default printer. We need it so that when some one who has already logged on before logs on its their default printer too and not the one they set as well as not just new users. We are on a large network of 400 Computers + and its not in our best interest to have to go around to every person who logs on to a computer and has logged on before to change it for them. One time Administrator type thing is what we are looking for that applies it to all existing local users.

Also, We can get it to add to all of their accounts and we can see it in the printers folder but its not setting as their default. It just adds it so they can see it but doesnt change the default setting.