Every school district board of directors is authorized to establish and operate summer and/or other student vacation period programs and to assess such tuition and special fees as it deems necessary to offset the maintenance and operation costs of such programs in whole or part. A summer and/or other student vacation period program may consist of such courses and activities as the school district board shall determine to be appropriate: PROVIDED, That such courses and activities shall not conflict with the provisions of RCW 28A.305.130. Attendance shall be voluntary.