43 Pa. Stat. § 68
Before a child under sixteen years of age, who is not a resident of this state, may be employed, permitted or suffered to work at any time in this state in any factory or cannery, or in any of the other employments specified in section one of this act, his employer shall have received a school requirement certificate, issued by the principal or superintendent of the school attended by such child or by the officer empowered to issue employment certificates for the school district of which such child is a resident, certifying the child's age, as recorded in the school records of the district of his residence or as established by such proofs as are required by law for the issuance of employment certificates, and the exact periods during which such child is required by the laws of his own state to attend school.
The employer shall in every case keep on file during the child's employment, accessible for inspection by any attendance officer or labor inspector of this State, the school requirement certificate of every such nonresident child employed by him.
It shall be the duty of every employer of such nonresident child to acknowledge, in writing, receipt of every school requirement certificate within three days after it has been received, and to return the certificate to the person who issued it within three days after termination of the child's employment by him.
It shall be the duty of every school principal of this State, and every person authorized by law to issue employment certificates, to execute, on request of any child under his jurisdiction seeking employment in another state or of the child's parent or guardian, a school requirement certificate, such as described in the first paragraph of this section, and send such certificate by mail to the proposed employer. There shall be no charge for this service other than the cost of postage.
43 P.S. § 68