Trying to create a button that changes images on the site.

Hello,
I am fairly new to square space but I am having trouble tackling what I am looking to use the site for.
I am an educator and I am looking to create an "achievement board" for my students to be able to look at and access while in class.  My goal with the website is to have a front facing page that has "grayed out" achievement images. So then when the class completes one, I will have the functionality on an admin page to mark that they achieved it and switch the image to full color.

I hopes of doing this I have tried looking up button functionality within a page but I keep finding ways to only change the image of a button. Nothing I see seems to allow the button to effect anything on the page itself. Could someone point me in the direction of creating a system like I am trying to achieve?