Because male high school students are boys and female high school students are girls. This remains the case until such time as an individual reaches the Age of Majority, which is 18. Afterward, they are legal adults, and thus entitled to being called "men" and "women".
"Almost 18" doesn't count.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.