Insane Steve speaks very wise words.
During the high school years, I believe people should focus their energy (aside from schoolwork and junk) on figuring out who they are, their identity, their goals and desires, what they want out of life. If you haven't figured yourself out, and especially if you haven't learned to love and value yourself, there's no way you can maturely handle a relationship. If you can't love yourself, you can't adequately love someone else, and you can't expect them to love you more than you love yourself. Only after one has done these things, when he or she is mature enough to handle one, should they then think about relationships.
A person cannot fill a void in you. You have to discover how to do that on your own. One needs to learn to be content as single before he or she should think about entering a relationship. A relationship should be formed on the basis that you love the person, and you want to have someone to love, not with the primary goal being because you want someone to love you, to be loved. Love isn't selfish, and if the latter is one's only or strongest desire, that's selfish. If you're selfish, you cannot adequately love another person. And if you can't adaquately love a person, you can't maturely be in a relationship. And if you can't maturely be in a relationship, you shouldn't be in one at all.
Also, I believe relationships need to be formed on the foundation of mutual and genuine friendship, love, care, and respect, not because "if I'm not in one, I'm a loser" or "everyone else is in one" or "well, I like him/her" or "I'm lonely." And if you like someone, try to figure out why it is you like them, why you're attracted to them.
In general, introspection is good. Figure yourself out, how your mind works, and grow from there.
On another note, realize that people generally aren't attracted to (or remain attracted to) people with low self-esteem and/or who are selfish. (Seflish being more concerned about one's self than others; however, caring more for others than for yourself is also unhealthy, as that leads to martyrdom and resentment. There needs to be equal balance.)
I have ANGST about the mentality most people seem to have regarding relationships, a very selfish perspective. I also have ANGST when people have low self-esteem. I want to knock some sense into them and make them realize that they have value, and they need to utilize their potential. If you don't like yourself, change your actions and/or attitude. It's all about how you perceive reality.
This is the first time I've posted in this topic.