That worked great!
I had to multiply the unSelectedSchools calculation by 100 to put it on the same scale (e.g., 57.6 instead of .0576) as the hard coded Performance in the data. Otherwise, it returned .576 (e.g., Jul - Jun value) which it saw as less than 0 and put the line at the bottom of the axis. I tried changing various formats for the axes and pill but it wouldn't move. I'm not sure how you avoided the * 100 multiplier.
My issue now is that I need to use the color legend with that graph (and about 15 other graphs for different metrics), but the blue box in the color legend is labeled "Selected Schools" whereas I'd like it to say the name of the actual school, in this case "Anne." (I renamed "unSelected Schools" to "Overall" so that piece is fine.) I read that dynamic legends aren't possible.
I realize I can put a floating worksheet with the selected school's name next to the blue box in the legend (i.e., on top of the "Selected Schools" label)? Is there a more dynamic, scalable solution? Otherwise, I have to add and position a floating worksheet over the legend for 15 other charts where I'm using this technique.