I don't follow high school sports all that much, but this isn't really a new thing. It could very well be more common now than what it used to be.
My high school team growing up was #1 in Iowa 4A for most of our senior year and top 5 the rest of it. Similar my junior year. We had our fair share of close games against other good schools, but many were blow outs. So bad that teams would hold the ball for several minutes at a time (not shot clock) just trying to play us into the lowest scoring game possible. It was sad to watch.