I'm doing a lot of activites in my senior year and I've already applied to colleges. Is there a way to let colleges know what I'm doing throughout senior year after I sent in my application?
Excellent question. Typically, you want to mention those things on the application. When my two young adults were in high school I assisted them with creating a one (1) page "BIO on their accomplishments over the years (9 - 12 grade); similar to a resume". It included everything they were involved in academically, sports, travel abroad, volunteerism, church, etc. They used that bio to "attach to their college application and interviews". Interviewers were highly impressed.
FYI, my son is a recent medical school graduate (5/2018), 1st year Resident Pediatrician; and, daughter 1st year Accelerated Math High School Teacher (5/2018).
They shared their "bio template" with family & friends, which are experiencing success with documenting accomplishments.
Good Luck to You!
If these activities are important toward your entrance to the college or potential scholarship eligibility at the college drop an email to your admissions counselor. They would be able to help you get it into your application file, directed to the right person or, suggest ways to highlight them in other ways. This is per my experience of 22 years as an admissions professional.
Jason recommends the following next steps: