It would be a huge cost saving approach - and then it will happen in other classes and more and more probably down as low as 4th grade.
Kids will have to go to a private school, or homeschooling, to get the experience that most of us had. In time, public schools will be for those who cant afford a private school or for those with disabilities that cant be accommodated in a private school.
It is hard enough to teach calculus online to 20 kids. You model simply won’t work.