Kitsap County sheriff's deputies said they were arrested Tuesday at Silverdale Elementary School after one of the boys was found with the handgun on school property, KOMO-TV, Seattle, reported.
One of the boys had asked the other to bring his parents' handgun to school so he could use it to assault members of his own family, deputies said.
The boy who'd been asked searched in his home and found the gun safe, investigators said, and found a key to the safe in the house, taking the .40-caliber semi-automatic handgun and putting it in his backpack.
On a bus bound for the school the boys showed the gun to other students, investigators said.
At the school news of the gun spread until it reached a teacher, who checked the bag of one of the boys and found the handgun.
The two boys were taken into juvenile detention for investigation of conspiracy to commit assault in the second degree, KOMO-TV reported.