Design product Rest api post method to accept data from multiple client

I need to define a rest api to accept data from different schools. When School post student information, I need to persist that information in data store. Unless I get school I’d or some identifier for school in post request payload, I will not be able to store school specific entities. I may need to Persist different entities per school and this api should work for all schools. Should I define post method payload for each entity and mandatorily add school identifier in each payload and each client should send this identifier in each request ? Is this correct approach? Identifying calling customer will help in executing specific logic like usage, tracking etc. How to design such an api?