you can have an option set on the page of type number and have a “when page is loaded” workflow that sets it. Put the calculation in that workflow. All the current users scores divided by the number of scores. Then you can reference it in a repeating group or wherever you want.
You could also do that option set as a list if you wanted multiple users average scores.
You might consider just working this calculation into whatever workflow records their individual scores and have it update the average each time. Then its saved in the database where it sounds like you want it.