Advice for a Daunting Role

Hi everyone.

Recently I got cast as Judas in a high school production of Jesus Christ Superstar. It's a daunting show, but it's a production involving lots of talent from many schools in a small city so we'll be able to pull it off.

The reason I'm posting this is because the role I got is especially challenging vocally, and as a high schooler I haven't had a lot of vocal experience. Although I have made it to national level in choral competitions, I usually sing as a baritone. I find it a struggle to stretch up to the high A's that Judas has to sustain in his songs, and often it sounds extremely shouty and strained, and I can feel it hurting my voice. I was wondering if anyone had advice as to how I should approach this character, in order to make it powerful and do it justice, but also sound good and be safe vocally.

Thanks!