Whenever a salary schedule increasing the salaries of its academic employees is adopted by a community college district to be effective at the commencement of the second semester of a school year:
(a) The compensation of the employees shall not exceed one-half of the annual compensation for their positions under the former salary schedule for services during the first semester.
(b) The compensation of the employees shall not be less than one-half of the annual compensation for their positions under the newly adopted salary schedule for services during the second semester.
This section shall not be construed to limit the time at which any salary increase ordered by the governing board shall become effective.