The department shall develop and make available technical guidance for reducing lead contamination in drinking water at schools that is at least as protective of student health as any technical guidance on this topic issued by the United States environmental protection agency. The technical guidance must include the technical requirements for sampling, processing, and analysis, including that analysis must be conducted by a laboratory accredited by the department of ecology. The technical guidance must describe best practices for remediating elevated lead levels at drinking water outlets in schools. Best practices must include installing and maintaining filters certified by a body accredited by the American national standards institute. Provisions of the technical guidance related to testing for the presence and level of lead in drinking water, as opposed to testing to identify sources of lead for remediation, must be designed to maximize detection of lead in water, and therefore must prohibit sampling or analytical methods that tend to mask lead contamination, including prestagnation flushing and removal of aerators prior to sampling.