Board Thread:Episode Discussion/@comment-4141313-20181215021300/@comment-4010415-20181217013220

ZeoCobra wrote: When I think about, there was no real reason for them to go to Haven academy, no one told them to go. Actually, this is incorrect.

You should rewatch the end of Ruby's scene with Qrow in End of the Beginning.

After Qrow explains silver eyes to Ruby and saying that there's something big going on, Ruby asks if she can help. Qrow tells her to rest and starts leaving the room. On his way out, he says "Besides, our enemy's trail leads all the way to Haven. That'd be quite a trip for a pipsqueak like you.", and he winks at her.

In short:

Qrow told Ruby to go to Haven in search of their enemy.

JNR tagged along, presumably to help Ruby with the task because they were personally affected by what Cinder did.