Keeping this in view, are high school relationships a waste of time?
Definitely not. You are gaining experience how to flirt better, how to kiss better also you are having fun with that girl. Some high school relationships are lasting very long, some are just few months, it depends on partners but definitely isn't wasting time.
Likewise, how long do high school relationships last on average? Most times it's more of a fling, which lasts for usually a night, sometimes one week. And then they'll never talk again but it'll haunt them forever. It sucks, really. But when you're actually in love (or at least think that you're in love), when you had at least 3 weeks to fall in love, it usually lasts 4–6 months.
Similarly, is dating in high school a good idea?
Dating in high school can be a really healthy and positive experience if the conditions are good. You don't have to date in high school and some of you may not even want to date and that's totally okay. Dating in high school is totally optional.
Why do most high school relationships fail?
Another reason high school relationships fail is due to the fact that to the people who are in them: teenagers. Those who care about themselves intentionally: These are the people who date because they want the relationship, not the other person in the relationship.