In all school districts wherein the provisions of Chapter 124 of the Revised Code do not apply, each board of education shall cause notice to be given annually not later than the first day of July to each nonteaching school employee, who holds a contract valid for the succeeding school year, as to the salary to be paid such school employee during such year. Such salary shall not be lower than the salary paid during the preceding school year unless such reduction is a part of a uniform plan affecting the nonteaching employees of the entire district. This section does not prevent increases of salary after the board’s annual notice has been given.