(1) Part B funds provided to school districts:

(a) Must be expended in accordance with the applicable provisions of this chapter;

(b) Must be used only to pay the excess costs of providing special education and related services to students eligible for special education services, consistent with this chapter; and

(c) Must be used to supplement state, local and other federal funds and not to supplant those funds.

(2) The excess cost requirement prevents a school district from using funds provided under Part B of the act to pay for all of the costs directly attributable to the education of a student eligible for special education services.

(3)(a) A school district meets the excess cost requirement if it has spent at least a minimum average amount for the education of its students eligible for special education services before funds under Part B of the act are used.

(b) The excess cost amount is determined in accordance with the definition of excess costs in WAC 392-172A-01075. That amount may not include capital outlay or debt service.

(4) If two or more school districts jointly establish eligibility in accordance with WAC 392-172A-06075 and 392-172A-06080, the minimum average amount is the average of the combined minimum average amounts determined in accordance with the definition of excess costs in those school districts for elementary or secondary school students, as the case may be.