Pub night used to score its beers on a 1-10 scale which led to many arugments as there was no actual defintion of what any of the values meant. CAMRA introduced a 6 point scale (0-5) as follows:
0 Undrinkable No cask ale available or so poor you have to take it back or can't finish it.
1 Poor Beer that is anything from barely drinkable to drinkable with considerable resentment.
2 Average Competently kept, drinkable pint but doesn't inspire in any way, not worth moving to another pub but you drink the beer without really noticing.
3 Good Good beer in good form. You may cancel plans to to move to the next pub and may seek out the beer again
4 Very Good Excellent beer in excellent condition.
5 Excellent Probably the best you are ever likely to find. A seasoned drinker will award this score very rarely.
On this site it has been proposed that we use the CAMRA scale with one slight modification:
-1 mean NO Real Ale
0 means Real Ale but not drinkable.
So why the difference? Simply because the CAMRA scale cannot differentiate between a pub that serves crap Real Ale and a pub that doesn't serve it at all. In most cases pubs that serve NO Real Ale do not have the facilities to store/dispense it. Pubs that serve crap Real Ale obviously have the facilities to dispense it, and presumably store it - even if they apparently don't know how to.
Pubs with a 0 score have the potential to move up the scale relatively quickly. It is only a couple of years ago that the The Restoration thought that serving Real Ale meant seving vinegar with islands of yeast floating in it. On the last visit the Restoration had several Real Ales all of which were in good form.