The Popularity Papers, Book Seven : The Less-Than-Hidden Secrets and Final Revelations of Lydia Goldblatt and Julie Graham-ChangAmy Ignatow2014

Lydia and Julie have been through many adventures as they navigated junior high, popularity, families, and friendship. In the final adventure in the series, the peaceful world of Hamlin Junior High is rocked when Lydia and Julie learn that they’re going to have to play host to new students whose school burned down.
The outside threat bands the Hamlin kids together against a common enemy—for a while. When the enemy gets their hands on Lydia and Julie’s notebook, no one wants anything to do with the girls. It’s the biggest threat to their friendship (and a pretty definitive failure of their quest for popularity), and it can only be solved one way. Two words: dance battle.

Titre original : The Popularity Papers, Book Seven : The Less-Than-Hidden Secrets and Final Revelations of Lydia Goldblatt and Julie Graham-Chang (2014)