Students are not their teachers' clients. Nor should we aspire to our students' someday achieving such a relationship with us. Client is a term both too pompous and too shallow to characterize the special relationship that under the best of conditions exists between teacher and student. No teacher gains an increment in prestige by referring to his or her students as clients. Non-adult students are rarely, if ever, clients.
Clients are people who have a choice to withdraw from the relationship.
They can voluntarily cease to be clients. Students from 6 to 16 do not have such a choice. Clearly, compulsory education laws do not create a clientele. The usual relationship between service-provider and client is a quid pro quo. Fee recompenses service.