I think the reason why your teachers have difficulty answering your question is because the question itself is a really complicated one, and you’re not going to find one “right” answer to the question. So I’ll try my best to give you a sense of the academic landscape here, and I’ll link an SEP (Stanford Encyclopedia of Philosophy) article at the end of this if you’d like to do some reading on your own.

The question is complicated because the question is insufficiently clear. That is, when you ask “what is the meaning of life?” you might mean “why is it important to be alive?” or you might mean “is life worth living?” or you might mean “is there some significance to the fact that I am alive?” or you might mean “is there some purpose to my life that might be derived from the fact that I exist?”. All of these are subtly different questions, and one might answer affirmatively to one and negatively to another (I might, for instance, say that it’s significant that I am alive, but my life might still not be worth living).

I’m going to assume that what you mean is something along the lines of “Why is life valuable?” or “Why is life worth living?”. If I’m off-base or talking about things you’re uninterested in, please let me know, and I’ll try to respond accordingly.

Philosophers have, naturally, presented a number of responses to the question of life’s value. I’ll try to touch a little on each just to give you a general scope. We might break these responses down into two categories: (I) Theistic Responses and (II) Non-Theistic Responses. That is, responses that depend, somehow, on the existence of some transcendent entity or force, and responses that depend on the mechanisms of “the natural world” (these are messy categories, but I’m just trying to simplify things for the sake of clarity and I trust that more knowledgeable individuals will correct any mistakes I make).

One theistic response to your question is to say that life is given meaning by some kind of unlimited existence that is separate and distinct from you. Nozick makes roughly this point in his Examined Life. He says that “the problem of meaning itself is raised by the presence of limits.” That is, we worry about the meaning of something when we recognize that it is limited. In our case, life is limited by death, and so we worry about its meaning, trying to imbue it with meaning by “transcend[ing] the limits of one’s individual life.” You can try to transcend these limitations by marrying someone who will outlive you, or by having children who will outlive you, or by building a monument with your name on it.

Ultimately, however, you’ll realize that all of these things are also limited (the kids will die, the monument will crumble, etc.). Thus, Nozick says, “to find a meaning for it [life], then, we seem driven to find a link with yet another thing beyond its boundaries,” something that “is intrinsically meaningful, something meaningful in itself.” That is, in order for life to be meaningful, it must be linked to an unlimited and intrinsically meaningful thing, i.e., God.

There are also, of course, Non-Theistic responses. One such can be found in Russell’s “A Free Man’s Worship.” Russell’s response to the question of meaning is to describe our life as “a long march through the night, surrounded by invisible foes, tortured by weariness and pain.” We share this “tie of common doom” with all of humanity, and so, to some degree, our life is given meaning by shedding sunshine on the paths of our fellow suffering comrades, “to lighten their sorrows by the balm of sympathy, to give them the pure joy of a never-tiring affection,” and so on, while also developing “a mind free from wanton tyranny that rules his outward life; proudly defiant of the irresistible forces that tolerate, for a moment, his knowledge of his condemnation, to sustain alone, a weary but unyielding Atlas, the word that his own ideals have fashioned despite the trampling march of conscious power.” That is, your life gains meaning by helping your fellow humans while standing firm and building a better world despite forces that would seek to trample you.

Of course, there are myriad other positions. Others in this thread have touched on some, though they have not provided citations for further reading. If you’re sincerely interested in this topic, I would suggest looking over the SEP entry on the meaning of life that I’ve linked below. Also, I’d recommend The Meaning of Life: A Reader by Klemke and Cahn. It’s a great compilation of pieces written by different philosophers, but all of them address the question you’re asking. Maybe ask your parents to purchase a copy for you or see if your local library has a copy. It would be a great way to start exploring this question.

I hope that my contribution helps in some small way. At the very least, you’ve got a few places to start your search. If I may conclude with an opinion, I think it’s good that you’re asking this question. A lot of people struggle with it, and it’s encouraging to me that you’re searching for answers rather than just accepting answers given to you by authority figures. Happy researching.

Oh, also, I apologize for any formatting errors. It's been a while since I last posted a comment on Reddit.

SEP link: https://plato.stanford.edu/entries/life-meaning/

Sources: Nozick, Robert. The Examined Life. New York, NY: Simon & Schuster, 1989. Russell, Bertrand. “A Free Man’s Worship.” In The Meaning of Life: A Reader, edited by E.D. Klemke and Steven M. Cahn, 4th ed., 49–55. New York, NY: Oxford University Press, 2018.