I was playing a game as talon top lane and i got 23/5/18 with 158 CS and a thresh was a support with 16/6/15 and 65 CS. The thresh got an S+ and I only recived an A+. I dont understand why I didnt get the S, like i did far better than Thresh and did about 50 K damage to the enemy team. Can anyone explane why I only got an A+? 
Quil Evrything1 votesbecuase supprots get to count assists and kills as the same. non-supports only count kills and cs doesnt matter to them.
and you didnt say how long the game was. If it was 40+ minutes, you didnt have enough cs
Sona Ping1 votesBecause you didn't play better than the Thresh and comparing yourself on a carry to the support is irrelevant. You aren't even playing the same champion in the first place.
Ęsdeath1 votesFirst off, let me tell you that Supports should never be compared to other lanes - Supports tend to have a different kind of evaluation from the Grading System, specially because what counts most are the assists, warding and kill participation.
I have to say that your score is great enough to obtain an S, although, the grading system evaluates everything and not just your K/D/A.
Whilst I can say your K/D/A is pretty good, I can't say the same about your CS if your game lasted around 30-35 minutes (or more). Generally, you have to understand that, the longer your game lasts the less your K/D/A will matter. Probably you will see that 5/0/19 with 500 CS in 55 minutes will be an S while 27/0/20 with 200 CS will probably be an A+ (of course it can be an S if you managed to accomplish your objectives - but farm can be the decision here).
Generally, I use a mathematical expression to know if my CS is "going as expected": (75 x (y/10)) where y is the time of your game (MINUTES) -> This simply follows the common sense of: 75 CS per 10 minutes - Of course you can do 100 instead of 75, if you really want to achieve an higher grade and if you farm pretty well, that might be applicable.
Anyways, just to show you my side, I got 20/3/4 (with Quadra included), got 128 CS in 30 minutes - That seriously didn't make my S (got A+). The expected farm was: (75 x 3) = 225 ... almost 100 CS wasted. And trust me, 50 farm can be the difference between A+ and S (ignoring S- in the middle).
