I checked with SPS Communications - all SPS schools are giving the SBAC.
There ARE some schools - for different reasons - that are postponing/suspending the testing to some other point during the two-weeks.
I was told a postponement could be, for example, for a high number of ill students in a single day or technical difficulties but it appears it means that there are a high number of opt-outs and they may be trying to contain that.
They do report a high number of opt-outs in high schools especially for 11th graders. I think this makes sense because high school kids are likely to have heard about opting out from multiple venues, and know how to get it done.
I could not find any info at SBAC on postponements.
Update: KPLU is reporting at least 150 students are opting out of SBAC at Garfield. Maybe we should have a contest for the school that has the most opt-outs. (I'll front the ice cream or candy bars.)