§ 3012-a. Elementary tenure area. Notwithstanding any other provision of law to the contrary, and except in cities having a population of one million or more, elementary tenure area shall mean kindergarten through grade six for teachers employed in such grade levels after the effective date of this section. All teachers holding tenure as of the effective date of this section in the kindergarten tenure area or grades one through six tenure area shall be deemed to hold tenure in the elementary tenure area as defined by this section.