I concur. I've always know it as a "RASS".
It's pronounced 'RAS... As in rasp without the P. You can listen to an audio reading of the pronunciation at www.merriam-webster.com ... But from my experience few teachers have the humor and good character to be able to appreciate being proven wrong.. So before rubbing her nose in it.. Make sure your victory is worth it to you ; )
Agreed, it's definitely pronounced RAS.