Finding a writing partner isn't about finding someone who makes you more hire-able. It's about finding someone who makes you a better writer.
Agencies are the best starting place for anyone launching a Hollywood career… even if you don't want to be an agent. Many networks, studios, and producers won't even hire assistants who don't already have agency experience.
Most teens aren't ready to sell material or navigate an actual screenwriting career. But that doesn't mean you can't begin preparing NOW.