30 students? In one class, maybe. Most high school teachers teach 5-8 classes, so it's more like 150 kids per day, give or take. And that's just the hour or so per day they get with the kid.
I'm only about 6 years removed from high school, and I don't think going after the "bad teachers" (depending on who you ask) has ever been the right approach. If I had a magic wand, I'd structure curriculums to be more relevant to the modern era. The math-science-english-etc format basically hasn't changed since the 40's or so, yet the world we live in is completely different. Kids will pay attention in school if you teach them something they find useful. Instead of blaming teachers, how about we make school less boring?