Hope is Made of Helium by Amy Zinn

On the first day of their senior year, the graduating class of Bigleaf High releases balloons carrying their greatest hopes into the sky. But when a freak cold front sends the balloons drifting back to earth, whoever reads what’s inside finds that wish suddenly coming true in their own life.

Hopes collide with reality.

Friendships are tested, secrets surface, and lives become tangled in unexpected ways as students are forced to live with the consequences of someone else’s dream.