The board of education of any school district may contract with the state department of education or other state agency or with any agency of the federal government for the education or training of out-of-school youth or adults regardless of their place of residence. The board of education may permit the attendance, under such contract, of such students or trainees who are not residents of the school district only if the contract provides for the reimbursement to the school district of the entire actual cost of educating or training such nonresident students or trainees and regardless of the ratio of nonresident students or trainees to resident students or trainees.