I've been running into several issues, the big ones are...
Java settings with Safari \- Finally got this one sorted out, but in Safari you need to run Java in "Unsafe mode" for the testnav site. I was able to deploy this setting with a config profile that is working on my 10.8-10.10 clients. The short version is to set the java settings correctly on a computer, copy the safari plist, then remove everything else that you don't want set, just leave the managed plugin policy for java/parcc. Export the plist as an XML plist and import into JSS. If anyone wants it I can attach the file I uploaded to the JSS. This has been working great, provided that the computer gets the configuration profile of course.
Second is the Java update prompts, make sure they're disabled or you provide instructions for teachers/students on what to do if they get the prompt.
Third is use a new blank profile when doing testing. The first trial we had some issues with programs the students had installed popping up and kicking them out of the test.
One issue that a teacher pointed out was that if a student right clicks on the test they can bring up the dictionary lookup, but if they click on it, it bumps them out of the test. Was looking into disabling right click for the testing user but haven't had much luck yet, anyone have suggestions?
Last is a bug in the test itself, I have had a few students get kicked out of the test when clicking the tools icon or going to the next section, in some cases multiple times in 10 minute window. We did get some feedback from the state/parcc that other districts were having this problem as well. Can anyone confirm that?