Alice, I'm not going to delve far into your thoughts regarding the old guy because we both know it's not gonna happen. The odds of him wanting to date someone who is barely an adult is extremely low.
Yes, High School guys can be immature and goofy. It's why many girls your age find themselves dating boys who are in their early 20's. The average girl does mature more quickly than the average guy. When you get to college and meet more people, your dating pool will open up.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.