By no later than 90 days after implementation of the guidelines and specifications established under Section 15 of this Act or thereafter when it is economically feasible, all elementary and secondary public schools and all elementary and secondary non-public schools with 50 or more students shall establish a green cleaning policy and exclusively purchase and use environmentally-sensitive cleaning products pursuant to the guidelines and specifications established under Section 15 of this Act. However, a school may deplete its existing cleaning and maintenance supply stocks and implement the new requirements in the procurement cycle for the following school year.
     For the purposes of this Section, adopting a green cleaning policy is not economically feasible if such adoption would result in an increase in the cleaning costs of the school. If adopting a green cleaning policy is not economically feasible, the school must provide annual written notification to the Illinois Green Government Coordinating Council (IGGCC), on a form provided by the IGGCC, that the development and implementation of a green cleaning policy is not economically feasible until such time that it is economically feasible.