I have been teaching students for 20 years (in NY) and a disturbing trend has grown in the last 10 years. Despite lip service to rigorous instruction, the expectations have been dropping on an annual basis. Social promotion as insured everyone who shows up to class and does little else gets promoted to the next grade. By the time these students get to high school, they either have strong foundational holes in their education or have just given up completely. What is the solution that the DOE come up with to solve this problem? They lower the amount of end of year exams that must be passed to graduate from 9 down to 5 (possibly 4). They removed half the material from the World History Regents, make the chemistry regents significantly easier and have a curve so large on the Algebra I state exam (in NY) that getting 35% of the questions correct, gets you a passing grade.
Assuming a 1 hour lesson, 5 times a week, that is 300 minutes divided by 30 students, for a total of about 10 minutes of individual teaching time per student. That is not enough time to learn the material for a large portion of students.
Tutoring on the other hand is a 2 hour session once a week focused at 1 student... so 10 minutes vs 120minutes. Tutoring is therefore 12x more effective.