Senior year Vs Junior Year

Hi
I was just wondering how this works.
Let’s HYPOTHETICALLY say I was a senior. I finished junior year and I did well. I sent all my applications already etc. What if I was a lot more successful in my extracurriculars during my senior year versus my junior year? How do I let colleges know of my success because it’s after I sent my applications in?
For example,
I won a national award. I also won 1st place in 6 competitions and qualified for an All State Choir ALL during my senior year. All of this is NOT in my applications because I turned those in back in November. These success stories would’ve really helped my applications/ECs etc but it’s too late. How am I supposed to notify the college that I succeeded in this, this, and that?

if you are applying to a private school, they look at all 4 years

Here’s what I hear-

  1. Adcoms are very busy people - so if you send an update of any kind, you need to make sure it’s actually important. If you won an Olympic Medal or a World Championship, that’s one thing. On the other hand, it’s not worth it to tell them that you got into the National Honors Society or some minor EC.
  2. HOWEVER, if you are deferred from a first choice college, people do send “letters (emails) of interest” to let them know that they are their first choice school and they may include some accomplishments from senior year. If you decide to do this, then you can mention what you accomplished during your senior year.