I have seen that there are digital test packets and CDs to purchase from SOINC - are they useful? My team might need them, but I'm not sure if we need them...at least for solar system, are the SOINC-purchase CDs/digital test packets useful? Thanks! - matematika
The National Test Packets - which contain tests from past national tournaments - are generally good. However, since this year's topic for Solar System is completely new, they would not be of much use. There are similarities between the current topic and the 2014 and 2015 topic - an experienced competitor may find it useful to look at 2014 and 2015 tests to figure out how the event works and apply the knowledge to preparing for this year's topic.
I can't speak to the CDs, since I rarely use them. It expect it would depend on the event.