(1) Beginning with the 2023 regular legislative session, and every four years thereafter, the legislature shall review and rebase state basic education compensation allocations compared to school district compensation data, regionalization factors, what inflationary measure is the most representative of actual market experience for school districts, and other economic information. The legislature shall revise the minimum allocations, regionalization factors, and inflationary measure if necessary to ensure that state basic education allocations continue to provide market-rate salaries and that regionalization adjustments reflect actual economic differences between school districts.

(2)(a) For school districts with single-family residential values above the statewide median residential value, regionalization factors for school years 2018-19 through school year 2022-23 are as follows:

(b) In addition to the regionalization factors specified in (a) of this subsection, school districts located west of the crest of the Cascade mountains and sharing a boundary with any school district with a regionalization factor more than one tercile higher, are regionalized by six additional percentage points.

(c) In addition to the regionalization factors specified in this subsection, for school districts that have certificated instructional staff median years of experience that exceed the statewide average certificated instructional staff years of experience and a ratio of certificated instructional staff advanced degrees to bachelor degrees above the statewide ratio, an experience factor of four percentage points is added to the regionalization factor, beginning in the 2019-20 school year.

(d) In addition to the regionalization and experience factors specified in (a), (b), and (c) of this subsection, the following school districts are regionalized by three additional percentage points:

(i) School districts located entirely in Pierce county with a regionalization factor below tercile 2 that border both Puget Sound and the largest school district in Pierce county;

(ii) School districts located west of the crest of the Cascade mountains that enroll between six thousand and ten thousand students and do not receive adjustments under any of the adjustments under (a), (b), or (c) of this subsection;

(iii) A school district in Whatcom county that borders both Puget Sound and a school district with a regionalization factor above twelve percent for all staff;

(iv) School districts located within the Olympic Peninsula, which for purposes of this subsection includes only districts located in Clallam, Jefferson, or Grays Harbor counties, that meet any of the following criteria:

(A) The two largest school districts within the Olympic Peninsula based on full-time equivalent student enrollment, excluding enrollment in alternative learning experience programs, among districts that did not receive adjustments under any of the adjustments under (a), (b), or (c) of this subsection;

(B) A first-class school district as defined in RCW 28A.300.065 that borders a district with a combined adjustment under (a), (b), and (c) of this subsection of at least ten percent for certificated instructional staff;

(e) Additional school district adjustments are identified in the omnibus appropriations act, and these adjustments are partially reduced or eliminated by the 2022-23 school year as follows:

(i) Adjustments that increase the regionalization factor to a value that is greater than the tercile 3 regionalization factor must be reduced by two percentage points each school year beginning with school year 2020-21, through 2022-23.

(ii) Adjustments that increase the regionalization factor to a value that is less than or equal to the tercile 3 regionalization factor must be reduced by one percentage point each school year beginning with school year 2020-21, through 2022-23.

(3) To aid the legislature in reviewing and rebasing regionalization factors, the department of revenue shall, by November 1, 2022, and by November 1st every four years thereafter, determine the median single-family residential value of each school district as well as the median value of proximate districts within fifteen miles of the boundary of the school district for which the median residential value is being calculated.

(4) No district may receive less state funding for the minimum state salary allocation as compared to its prior school year salary allocation as a result of adjustments that reflect updated regionalized salaries.

(a) "Median residential value of each school district" means the median value of all single-family residential parcels included within a school district and any other school district that is proximate to the school district.

(b) "Proximate to the school district" means within fifteen miles of the boundary of the school district for which the median residential value is being calculated.

(c) "School district employees" means state-funded certificated instructional staff, certificated administrative staff, and classified staff.

(d) "School districts in tercile 1" means school districts with median single-family residential values in the first tercile of districts with single-family residential values above the statewide median residential value.

(e) "School districts in tercile 2" means school districts with median single-family residential values in the second tercile of districts with single-family residential values above the statewide median residential value.

(f) "School districts in tercile 3" means school districts with median single-family residential values in the third tercile of districts with single-family residential values above the statewide median residential value.

(g) "Statewide median residential value" means the median value of single-family residential parcels located within all school districts, reduced by five percent.