Ender’s Game is the first book in Orson Scott Card’s Ender Wiggins series. The story follows Ender, a pre-teen boy who has been tapped as a future commander for Earth’s space army fighting against alien invaders. Early in the book he is sent to a space training academy where he and other children are trained to fight in “battles” – physical tactical games that take place in zero-gravity. Right before the battle your question references, Ender has been promoted to Commander of a newly formed Dragon Army, with untrained members who have little to no skill in the battle room.
The teams that win battles are ranked on a board in the lunchroom, but Orson Scott Card doesn’t make a note of the team’s ranking, but rather of Ender’s. During Dragon team’s first battle with Rabbit Army (a much better army), Ender uses his tactical skills and unconventional tactics to win the battle, surpassing expectations. At the end of battle, Ender has the best Commander Ranking in the school. He has a perfect win-loss record and he/the team is ranked first in average soldiers-disabled, average enemy-disabled, and average time-elapsed-before-victory. There may be other categories, but those are the ones Orson Scott Card mentions by name.
For more information or other questions on the book, check out the eNotes study guide, linked below.