Public pc network access management

Hi, hoping someone might have some ideas of how to overcome this problem I have.

Im after a software utility or some equipment that can give me some control over public access of my network. I won't go into to much details, but I want something that will deny network access and communication to and from pulic computers untill I give permission to do otherwise. Simply putting them on another network doesnt solve my problem as the "public" computers can talk to and from each other, which is not what I want.

Hope this makes sense. Feel free to ask more questions if need be.