And how much time do you actually think is wasted on dealing with disruptive students? 10% of the day? 35%?
To me, this sounds like a recipe for creating an upper class of uncreative, poorly-rounded conformists and a lower class of people who are undereducated and permanently pissed off at the society that fails to serve their needs.
I think it's pretty unlikely that this would be a substantial improvement in modern American society or many others.
Kids misbehave at school for a huge number of reasons (many of them socioeconomic but definitely not all), and it's not really the public school system's responsibility to fix that, but it is the school system's responsibility to give them an education so that they can properly integrate into society as an adult. Shoving the problematic students to the side exacerbates this.
Bonus points if the education system can encourage more independence of thought and action, creative and analytical problem skills, and the tenacity and wisdom that come from actually having gotten some hard things done.
A better system would be one that is more capable of demonstrating the value of education to the students (incentivizing them to learn, and making learning at any level more rewarding), as well as one that can accommodate a larger degree of student interests and learning styles. I don't really know how to do this without having more internships and so forth, which aren't necessarily feasible for younger children but may be for teens. Maybe somewhere in the world or at some point in history this has been practiced more?