How should I update colleges on extra curriculars?

I have an international level extra curricular that I really want to update colleges on since I feel it will help my application. My counselor asked me to write a few paragraphs on the activity and said he will email that write-up to colleges.

The reason I'm asking is that some colleges like Stanford have stated that they do not accept any unsolicited email attachments or application materials via email. Since my counselor is emailing them, would it make a difference or should I update them through other channels?

Your guidance counselor (or you) should try to get in touch with the admissions office and ask them directly what the best course of action is. I wouldn't recommend sending updates via other means just yet. The treatment of situations like this is up to the discretion of each individual institution.

You should also think carefully about how this extracurricular will help your application. How does it fit into the narrative of your other achievements in high school? Do you think it will really have a strong positive impact on your chances, or are you just throwing it in there as an add-on? You should only proceed with notifying schools if you've expended a lot of time and effort on this extracurricular and it's closely connected to the subjects or activities that represent your strongest interests.

If the update you want to give doesn't represent a truly dramatic change in your status within this extracurricular activity, you might think twice about bombarding colleges with additional write-ups.