Each district's annual student transportation allocation shall be determined by the superintendent of public instruction in the following manner:
(1) The superintendent shall annually calculate the transportation allocation for those services provided for in RCW
28A.160.150. The allocation formula may be adjusted to include such additional differential factors as basic and special passenger counts as defined by the superintendent of public instruction, average distance to school, and number of locations served.
(2) The allocation shall be based on a regression analysis of the number of basic and special students transported and as many other site characteristics that are identified as being statistically significant.
(3) The transportation allocation for transporting students in district-owned passenger cars, as defined in RCW
46.04.382, pursuant to RCW
28A.160.010 for services provided for in RCW
28A.160.150 if a school district deems it advisable to use such vehicles after the school district board of directors has considered the safety of the students being transported as well as the economy of utilizing a district-owned passenger car in lieu of a school bus is the private vehicle reimbursement rate in effect on September 1st of each school year. Students transported in district-owned passenger cars must be included in the corresponding basic or special passenger counts.
(4) Prior to June 1st of each year the superintendent shall submit to the office of financial management, and the education and fiscal committees of the legislature, a report outlining the methodology and rationale used in determining the statistical coefficients for each site characteristic used to determine the allocation for the following year.