All spellers will receive the 450 Word Study List, including definitions--this is the best place to start for School-Level Spelling Bees.
There is also a new Spelling Bee App and other resources on their website: https://spellingbee.com/parents.
Words of The Champions contains a total of 4,000 words, including the 450-word School Spelling Bee Study List. Words of The Champions is divided into One Bee, Two Bee and Three Bee difficulty levels--this is a great extension for spellers who've mastered the 450 words and hope to advance to the District or Regional Spelling Bees. Any word on this list may be asked in competitions taking place beyond the school level.
Remember, although spelling bees begin with words from the study guide, they often end with words you haven't studied.