Prohibits a variety of weapons and dangerous objects on public or private elementary or secondary school premises, school-provided transportation, or areas of facilities while being used exclusively by public or private schools, and prohibits possession and use of any object, implement, or instrument that has the capacity to inflict death or substantial bodily harm when the use, attempt, threat, or intent is of a nature likely to inflict death or substantial bodily harm.

Requires the superintendent of public instruction to convene a multistakeholder school threat assessment work group to develop a model policy and programmatic guidance on threat assessment and threat management in schools.

Requires each school district board of directors to adopt a policy on threat assessment and threat management in schools that addresses how schools will provide for the safety of all individuals involved in or affected by threats of violence or harm, or the use, attempted use, threatened use, or intent to use a firearm or other weapon prohibited under RCW 9.41.280.