To be told that any group of years in your life should be the best few years of your life is kind of a let down.
This isn't to say you shouldn't enjoy as much as you can, but it discredits years ahead that could be filled with far better things.
Like high school.
Honestly, high school was somewhat lacking. Maybe I was in that phase that a lot of teenagers get, where no matter where they go, they don't belong. Or just angsty. Either way, high school was not, and never will be the best years of my life. Granted, in some ways, it was definitely easier, but that doesn't make it necessarily good. High school gave almost no homework, even on an AP track, but academically I learned very little. People tend to really suck in high school too, hormones are flying is one excuse, but sometimes people are just really scummy. Other's are trying to learn who they are, and others know who they are and use it to their full advantage. Don't take it to heart, only time will show them who they are and how they got to be who they are.
For example, my hometown is one of those small cities that unless daddy was a big wig or knew someone, chances were you were just a face in the crowd and mostly overlooked. Unless you were in that elite group, you were a one of the masses. This probably happens everywhere, but where I lived it completely ruled the school.
Then there's dating in high school which can be fun, but there's almost always an expiration date on it. Besides that, people change way too much in the few short years of 14-18, and I really would rather not have people remember exactly what I was like in that span of time.
College also shouldn't be the best few years of your life. Any time can be a great time, but realistically think about where you are and what you are doing. Maybe you don't have to pay rent yet, or worry about a job. Maybe you party every weekend and not worry about a thing. But don't sit there and tell yourself, "This is the best time of my life."
You're simply discrediting the times ahead of you. There's more to life than high school football games, there's more to life than winning beer pong. There's groundbreaking research, there's holding your first child, there's getting your first promotion or pay raise. There's buying your first house, or your first apartment and actually living alone with your cat/dog/guinea pig.
However, adulthood is not monolithic, and not everyone experiences it the same way. Experience what you want, how you want. Don't let someone tell you in what order the "best years of your life" should be in, or if you should even have those alleged "best years."
Study broadly. Don't narrow life choices because there's one thing that you think you'll want to do forever, do everything you can. Do things you probably can't. But don't let time fly by without acting on it, especially if you're willing to label it "the best years of your life."