RCW 28A.400.230

Any school district authorized to draw and issue their own warrants may deposit the cumulative total of the net earnings of any group of employees in one or more banks within the state such group or groups may designate, to be credited to the individuals composing such groups, by a single warrant to each bank so designated or by other commercially acceptable methods: PROVIDED, That any such collective authorization shall be made in writing by a minimum of twenty-five employees or ten percent of the employees, whichever is less.