Sec. 12. Formal collective bargaining between a school corporation and the exclusive representative shall not begin before:
(1) September 15 in the first year of the state budget biennium; or
(2) September 15 in the second year of the state budget biennium if the parties agreed to a one (1) year contract during the first year of the state budget biennium or the contract provides for renegotiating certain financial items the second year of a two (2) year contract.
Informal negotiations may be held before September 15.