(a) General. A public agency must ensure that a reevaluation of each child with a disability is conducted in accordance with §§ 300.304 through 300.311—

(1) If the public agency determines that the educational or related services needs, including improved academic achievement and functional performance, of the child warrant a reevaluation; or

(2) If the child's parent or teacher requests a reevaluation.

(b) Limitation. A reevaluation conducted under paragraph (a) of this section—

(1) May occur not more than once a year, unless the parent and the public agency agree otherwise; and

(2) Must occur at least once every 3 years, unless the parent and the public agency agree that a reevaluation is unnecessary.