Face Time
I suggest a more direct approach: face time. On the assumption that your student can only listen to one teacher at a time, let's itemize that instead, and see what that costs.
A high school student (OK, me, 1966), for example, has 6 one hour classes. Class size is about 24. Average teacher cost is $55,000 including benefits. Teachers work 5 of the 6 periods, so each teacher produces about 120 student-hours. Each student consumes 6 hours, requiring 1/20th of a teacher, which is $2,750.
Average spending is typically $10,000 per student total. We are told that 15% is non-payroll, so we have $8,500 payroll. Subtracting the face time teaching leaves $5,750 per student going to people who have no instructional face time with your student.
Yes, there are janitors, bus drivers, cooks, coaches, librarians, and office help to pay. There is general supervision to pay, and counselors and nurses. But show me a business where the "G and A" (general and administrative) expenses are even 50% of an professional employee's salary and benefits.
This is the dialog we truly need to have: where is all that non-face time going?