I bought a home on a land contract, owner holding deed. Who is billed the school taxes? Who then is billed the deed holder or the buyers on the landcontract? NY State

Generally a contract for deed means that the seller retains the deed AND ownership until the contract is completed. So the owner is billed for and responsible for paying the taxes. The contract may require that the seller pay the taxes, in which case the seller can bill you for them. But you would have had to agree to that provision in the contract.

If the seller does pass the cost of taxes on to you, you would not get the real estate tax deduction because you are not yet the owner.