password protection (yes, I did search!)

I am having a hard time with this, so please forgive me if it’s an easy fix (I will be delighted if it is!)

I am running a blog for my grade one class. I want the entire blog to be password protected, but I don’t want users to have to register or anything like that.

what I want, is for them to type in the address, have a screen pop up saying “please enter the password”, they enter it and voila, normal blog.

can this be done? I’ve searched help and plugins and found many different variations on this, but none that match my requirements…which seems odd.

thanks!