Okla. Stat. tit. 70 § 15-106
Any school district that is authorized by law to provide transportation for pupils to and from school may become indebted for the purpose of purchasing transportation equipment and may issue its bonds, as provided for by law, in any amount not exceeding, with existing indebtedness, ten percent (10%) of the valuation of the taxable property within the school district, as shown by the last preceding assessment for state and county purposes previous to the incurring of indebtedness. The bonds shall be made to mature within a period not to exceed five (5) years from their date. It is hereby declared that the use of the word "equipment" in Section 26, Article X of the Oklahoma Constitution was intended to include the "transportation equipment" referred to in this section.
Okla. Stat. tit. 70, § 15-106