Why reach out to a professor in high school?
A professor can show you what real research looks like long before college does. A summer in a lab, a mentor for a science fair project, or a single conversation about a paper you read can change what you decide to study. It can also give you something concrete to write about in applications, beyond grades and test scores.
The hard part is not wanting to do it. It is finding the right person. Most university sites list hundreds of faculty, and most of them work on things far from your interests. Searching by topic and by city turns that list into a handful of people who actually publish on what you care about and who are close enough to meet.