Some times a bill could be catagorized in more than one way. DREAM act addresses both immigration reform and Education and thus could actually be in both committe.

It is common for one bill to be in different committes.

Well, does it have a significance?

Depends how much you read into it. I would say not that much of significance. But It could be seen as a political move to ensure DREAM act to come up by itself if the CIR does not.

So if CIR does not make it to the floor, DREAM act as standalone ( or attached) education bill could still have a chance.

They could probably do similar things to other immigration related bills if they decide to do them piecemeal.