This is a well-known concept called the "flipped classroom" and it works excellently. Because the time a student NEEDS a teacher the most is when they are actively struggling on a problem.
This is the correct answer and is being used by teacher friends of mine with great success.
The structure they chose is in-class work counts for 80%+ of their grade. All work in class is done with pencil & paper. Quite simple in fact to solve a large part of the homework cheating issue.
that does mean that there is less classroom time devoted to lecture or other activities though if the teacher is supervising drills and group work, but it might be the only realistic way to proceed
- when students come to the classroom, before assigning them work, have them place their cellphones at the teacher's table
- then give them homework, as simple as that