Tips for subbing high school?

Does anyone have tips for subbing high school? i have been subbing for almost a year now and i have never subbed high school before. One district i work for goes back Wednesday Aug 6th and i just got an assignment for this friday. I only usually ever do preschool-7th grade and i feel like 7th grade was pushing it! They terrify me as a 23 yr old 🤣 Im nervous but i haven’t worked the whole summer so im definitely not passing this assignment up. Any tips would be super helpful. I am a super soft spoken person and when the kids get loud i really struggle to raise my voice loud enough to get them to quiet down.