Senior year.

VR
I have so many questions about senior year, and I don't have anyone to ask about them. My mother didn't graduate with her class, and went straight to her GED in 10th grade. My father was in Mexico for all his life up until he was in his late teens, so everything they do there is different from here. I have one friend, and my boyfriend that are both in their senior years, too. 
So, are senior pictures a have to, or are they just if you're havin a graduation party? If they're a haveto, how do I go about it? Do I "rent" out a photographer, and find a place I'd really like my pictures done, or what? 
Any other tips would be great about senior year. Thank you! 
UPDATE: thank you to everyone for helping me! If I get my way, I won't be doing the poses, but just the formal. Thank you! 😊