Creating a site login to control access

Hello,

I am looking to put a login page in my site where I will have a group of members who will login with a single UN/PW. I do not want them to be able to change the PW, nor view any dashboards. They simply need to be able to login and logout.

I have tried a few plugins but they all still give the Subscriber-level user access to the dashboard or a profile that they can change.

Any help on how to accomplish this would be greatly appreciated! ??