Is it possible to get sent to Airborne School as a 12B in the National Guard?

As a NG Soldier it will depend on the following:

1. MTOE (authorized positions within the unit).
2. Funds.

Units in the NG normally lack the resources ($$$) to send their soldiers to this type of training. They have to focuse on required MOS and Leadership training opportunities.

Your best bet would be to join a SF unit, which doesn't have 12B unless you were to become an 18C, or you'd have to be a support MOS for that SF unit (such as a cook, mechanic, supply specialist, etc). Your other option is to join an Airborne NG unit. There are companies in RI, Texas, and Alaska. SF units are in Washington, West Virginia, Ohio, Rhode Island, Colorado, California, Texas, Utah, Alabama, Mississippi, Florida, North Carolina, Illinois, Kentucky, and Massachusetts.

Another option is once you've gone to your unit, participate in the Best Warrior competition. If you advance past the battalion level, there's a good chance your BC will send you to the school of your request, Airborne, Air Assault, etc. If your unit doesn't participate in best warrior (much like mine), speak to your peers and see if anyone else is interested, you might be able to ask your command (using the proper channels of course) if they'd be willing to start a competition or if they'd be willing to send you to the BN competition.

Other than that, as Major Rivera said, your chances are slim in a reserve component.

Larry Fajardo Make sure it is in your contract.

https://www.goarmy.com/soldier-life/being-a-soldier/ongoing-training/specialized-schools/airborne-school.html