Dear [Recipient's Name],
Hello! I hope you are doing well. I just wanted to send you a quick note to say hello and share some of the fun things I have been up to lately.
I also joined the [School Club/Activity] club and we have been doing [Activity] every week. It's a lot of fun and I have made some new friends.
How have you been? What have you been up to? I would love to hear all about it.
Warm regards,
[Your Name]