It depends on the area, the league operator and some other factors. I myself am a SL7 in APA 8-ball, but a SL6 in APA 9-ball. In my opinion I shouldn't be one, especially with only being at 50% 8-ball for the session across all my teams and only having 50% lifetime wins. According to my LO, the reason for bumping me up was that I consistently beat other 6's & 7's. Which in my opinion is a crock of s*** because it doesn't take into account the others that are having a bad night or sandbagging their skill. It sucks really because my teams are the ones who are now punished with having to work around my SL7 status. And yet, I know a TON of 5's & 6's that would either beat me or give me a run for my money. I was essentially told (without these exact words) to suck it up and accept that im a 7 now. Im totally fine with being one, just not at the expense of hurting my teams.
EDIT: USAPL is suppose to be starting in my area soon so I hope that picks up because then we will have something that is fargo rated and not this dumbass APA equalizer system.