As long as the firearm is locked in the vehicle and out of site you are allowed to have it in your truck on k12 grounds. Since you have a CPL there is no requirement to unload a pistol but rifles must be unloaded if memory serves correct anytime they are in a vehicle.
As far as the College it appears that the WAC's keep you from having a firearm at all on any college property, mind you the rules are different for each college. Look at this WAC, http://apps.leg.wa.gov/WAC/default.a...e=132C-120-100, and it tells you the jurisdiction that 132C has. Since firearms are disallowed under http://apps.leg.wa.gov/WAC/default.a...e=132C-120-065the college says it is a no-no to bring them on any property owned by the college or at any collegerelated activity or function.