As a general rule, there isn’t the craziness discussed in that article in prep school, because it IS harder to micromanage from afar. There isn’t the parental involvement in playing time etc you see on the sidelines of public schools/clubs.
That said if the family is mega wealthy I’m aware of one example of that micromanaging – for one kid the family hired a private tennis coach, bought a house near the school for him, and had him give private lessons to their child, as well as help coach the school team (if I’m remembering correctly). This family also got the kid’s first novel published while at the school. For their daughter they would have their private jet stand by to fly her down to Florida to compete in horse shows. But this was a complete outlier in terms of what families do/did.