Do you have to play the clarinet before doing bass clarinet?

Band teachers almost always want you to play Bb clarinet first. The reason is you need to get used to the embouchure (mouth position) on a more natural feeling mouthpiece before you play a giant mouthpiece.

I guess it wouldn't be absolutely necessary to play b flat clarinet first, but my guess is that it would make playing the bass clarinet easier. All of the bass clarinet players I know started on the b flat, even if only for a little while. But there's no harm in trying the bass first, I can't see any reason why you wouldnt be able to play it.

You don't have to, but it would be to your advantage to get a little experience on the smaller instrument before you transfer to the bigger Bass Clt. Remember that the Bass Clt. requires more air-flow and is technically tricky to play in the high & low registers...Reed Guy