Like all teachers on the internet, I use standard based grading with my classes. I'm at the point where I would never go back and my math department is having success deploying it to most of our academic level preps. Every time I grade tests though, one little bit nags me. Though the idea of SBG is to move us towards learning for learning sake, at the end of the day, I have to assign grades. I use a 0-4 scale that translates into 0-80 (with a 4+4=5, and 5=100 context). The level that really nags me is the 3, a 60% on the scale, and I have a little modification where 3+3=70. Ideally, the scale should feel like this:

There's a nice, relaxed transition between each level. Mastery is clearly identified at one end, and deficiences at the other. A kid should be able to quickly look at their scores and see how they're faring. I really only give a 0 for leaving it blank, 1 for minimal effort, 2 for taking the first step at least once, and 4 for absolute correctness or minor mistakes. But then there's 3. How do you define being at a 3/5 proficiency level? Doing 3 out of 4 problems flawlessly with the 4th blank, that's easy. But what if all four problems are attempted, and the same error is present in all of them? What if all problems are attempted and there's a major error in just one? What if it's very clear the student understands the first step, but may not be clear with the conclusion, or wasn't quite sure how to interpret the answer? What if they did one part of the directions flawlessly but forgot to write a complete sentence like you asked, even if you're 1000% sure that kid probably just forgot and does indeed know how to answer it?

That's where the scale starts to feel like this:

The 0, 1, and 2 levels are very identifiable. And 4 should be special, leaving this HUGE gray area to be covered by 3. But do all those scenarios really represent 60% mastery? This isn't a huge problem in Algebra, the skills are defined clearly enough to where there's not a lot of interpretation to be done when I grade. But when I grade Pre-Cal it happens ALL THE TIME. One kid's 3 feels like sweet glorious mercy and another kid's 3 is due to unfortunate technicalties even if I know they know the material. The topics in Pre Cal are so much denser that I have a lot of students who can show me the math but can't quite handle the interpretation, or forget a niggling detail on all of their graphs. What's the solution? Go from 0-8? Where 8+8=10? What about 9? At a certain point that slippery slope gets you right back to grading things out of 100.

Perhaps the answer lies in putting the gradiation right where I need it, at the 3 level:

I can show a little mercy on the kids who have a clear grasp on the beginning but not the end with a 3-, and reward those who are clearly showing proficiency minus a labeled x-axis with the 3+. Perhaps 3- = 50/55 and 3+ = 70? And I scrap the double three rule and go with double 3+ = 75?

I could also scrap the 3- concept and just include 3+. It's worth experimenting with. Although I feel like with as many topics as I have within a six weeks that these things aren't really costing a kid the difference between an A and a B on a report card all that often. And any SBG system should be simple and transparent to avoid all the junk that exists when debating the differences between an 82 and a 86.

Perhaps it becomes a special Pre Cal rule? Time will tell.