If you do not know the answer, and for some reason you think that you should know, then you have a powerful mind that seeks answers. Congrats.
The truth is, very few people know what the cash equivalent is of one year of education. Proponents of vouchers, school choice, private schools, charters, etc, generally like the idea that every family receive the value of one year of education in a public school in the form of a certificate. The family can then take that certificate, decide which school to send their child to and then give that certificate to the school. The government would then pay the school the amount of the certificate.
Think of the following scenario. The average cost of education one child for one year in Oklahoma is around $10,000 or so. That's cheap, you say. It seems that way. But, in my first grade class in Broken Arrow, Oklahoma there were 32 students. If each student cost about $10,000 to educate and if each student were issued the certificate for that amount, then technically the school I attended would receive $320,000 in one year (9 month period in the case of many public schools) to educate one 1st grade class. The teacher was paid around 30-40k. Where did the other $290,000 go? To school lunches? Music class? Janitors? Hall monitors? Administrators? Union dues?
There's a problem here. I spent 90% of the time with my teacher who performed 90% of the services the school provided to me. But, he or she received only 10 to 12% of the value of the service provided.