Maybe this is on the more technical side of things and not the easiest read for a high schooler, but in my research field(s), every few years an opinion piece will be published that outlines the major questions in the field and a little about the importance/current progress. Both are free to view without paywall.
The one for biology (language is a quite technical): https://www.sciencedirect.com/science/article/pii/S0079610715000115
The one for chemistry (well written for a general audience, skip to pg. 7 for the good stuff): https://gmwgroup.harvard.edu/pubs/pdf/1241.pdf
These pieces provide a little bit of insight into why academic researchers do the work they do, and how exactly science and the search for understanding helps to change the world.
When I was a high schooler there’s no way I would have thought quite so deeply about global problems, nor would I have known where to begin. I just knew I loved reading about how things worked and asking ‘why?’ I bought old med/bio/chem textbooks from the library discard piles and tried to read and comprehend as much as I could (usually not all that much, but maybe some osmosis happened). I remember being fascinated with brain chemistry at some point, then viruses, then prosthetics…
The biggest questions of public relevance are also correlate well to the ones that are most funded by the government. There’s huge push to understand Alzheimers disease and find a treatment- there have been some pretty prominent disappointments in pharma for Alzheimers treatments in the past few years. The cancer moonshot, better batteries strong/large enough to power entire communities and hold the energy collected during the day from the sun, ways to artificially close the CO2 cycle so we can use CO2 as a source of fuel (aka. artificial photosynthesis), controlling pain without opioids, etc. Unfortunately, the media doesn’t write about scientific research in a compelling way most of the time, so it’s hard to read the news and appreciate the value of research.
My favorite places for reading about science in very accessible language:
Science Daily
Scientific American
Aeon