Before listing the majors and their Riverdale character equivalents, I must warn you that spoilers may lie ahead. Also, I only included the main teenage characters.
1. Political Science (Poly Sci)
Let's start with the guy that caused the most mystery in season one (besides his killer!). Jason Blossom would definitely be a political science major. Why? Because he was popular despite his highly unlikable family, and he was captain of school water polo team. From captain to president of America? Could Jason Blossom do it? Well, we'll never know now, but I'm sure he would run for some type of candidacy, even if it's just for class president.
ALSO: Get the pun? Poly sci? Polly Cooper?
Jason's next-to-kin, Cheryl Blossom would be a psychology major. After all, she is the queen of crazy. *Spoiler alert* Especially since she did burn her house down and threatened to kill her mommy dearest.
Everyone's actual favorite redhead, Archie Andrews, would be a communications major. He can make connections possible, even if by terrible means (Ms. Grundy and Clifford Blossom), or decent means (Josie and the Pussycats). Also, his knowledge of sports could make him an excellent sports broadcaster.
Archie's closest bro, Jughead Jones, would be an English major. This is definitely the most obvious considering that he is a writer, knowledgeable (his references are out of this world), and a deeply troubled soul (must I bring up his "I'm weird. I'm a weirdo" speech?) / Riverdale's very own Holden Caulfield.
For Betty Cooper, the most obvious answer would be Journalism. However, due to her straight-A grades, miss-I-can-do-it-all attitude, and organization skills, she would be a shoe-in for business.
6. Criminal Justice
Kevin Keller, obviously, would be a criminal justice major. He would definitely follow his dad's footsteps. After all, he is deeply invested in the murder of Jason Blossom.
Lodge women know how to negotiate. Good negotiation and business skills can work wonderfully for an economic major, so that would definitely be the best subject of study for Veronica Lodge.
Josie McCoy sunk her claws in music years ago when she formed her band, Josie and the Pussycats. Her ferocious love of sounds, feminist representation, and singing makes her a fantastic music major candidate.
Last but not least, Polly Cooper would totally be a nursing major. She might not be the brightest, but her natural joy and love for others will take her far in the degree.