See thread on Apple Support Discussions here if you want the techie side of this).
If you currently can not run PowerSchool GradeBook due to this issue, please put in a tech request on the district website.
The tech team is currently investigating this issue and will update you here.
UPDATE: (7:55am): Tech team is updating computers with this issue. Please put in a tech request if you are still unable to run PowerTeacher.
UPDATE (5:15am): Note from Pearson:
UPDATE (2:02pm): Looks like our first tests of the developers version of Java was a success. The tech team will test a few more machines, then roll out to all that have submitted a tech request.
UPDATE (1:18pm): From the forums we have read, Apple has disabled Java on all Mac's and it has nothing to do with the last version you may or may not have updated to. Apple has an internal blacklist in the OS - and all current versions of Java are included. Again, you can read more on the links I posted in the 12:58pm update.
UPDATE (12:58pm): Tech dept testing possible patch to java. Also, more on Apple's Java blacklist here (MacRumors) and here (another Apple discussions thread).