Summer's over, and Alexa and Katie are starting their senior year. They've been through so much together — but there's still more to come.

Junior year is finally here for Alexa and Katie with new relationships, surprising friendships and big decisions on the horizon.

For best friends Alexa and Katie, sophomore year brings budding romance, a birthday milestone -- and big lessons they'll never forget.

Alexa is battling cancer. But with her best friend, Katie, by her side, she's also starting high school -- and ready for whatever comes next.