Similar experience here. I went to four high schools. The best ones, academically, were the bog-standard schools that people love to use as an easy punching bag.
The ones where classes were a breeze and barely challenging at all were the private college prep school and the not-quite-as-rich-but-still-pretty-wealthy high school in the suburban white flight community. My read on the situation was that teachers had figured out that every single parent believed their kid deserved a constant stream of gold stars, and had the leisure time and resources to make their lives miserable until it started happening. Also the white flight school cared a lot about its football team so you better make for damn sure that the classes aren't so challenging that the quarterback has trouble balancing their time spent on homework, practice, and partying.
The ones where classes were a breeze and barely challenging at all were the private college prep school and the not-quite-as-rich-but-still-pretty-wealthy high school in the suburban white flight community. My read on the situation was that teachers had figured out that every single parent believed their kid deserved a constant stream of gold stars, and had the leisure time and resources to make their lives miserable until it started happening. Also the white flight school cared a lot about its football team so you better make for damn sure that the classes aren't so challenging that the quarterback has trouble balancing their time spent on homework, practice, and partying.