(a) A school district shall employ each classroom teacher, principal, librarian, nurse, or school counselor under:
(1) a probationary contract, as provided by Subchapter C;
(2) a continuing contract, as provided by Subchapter D; or
(3) a term contract, as provided by Subchapter E.
(b) A district is not required to employ a person other than an employee listed in Subsection (a) under a probationary, continuing, or term contract.
(c) Each board of trustees shall establish a policy designating specific positions of employment, or categories of positions based on considerations such as length of service, to which continuing contracts or term contracts apply.