Answer: Article VI, Clause 2 of the US Constitution (commonly known as the Supremacy Clause) requires that federal law be followed. That constitutional language is:
“This Constitution, and the laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any State to the contrary notwithstanding.”
In this case, the conflicting state law is superseded by the McKinney-Vento Act, and the child must be enrolled in school immediately. As you know, the McKinney-Vento Act is clear:
“(C) IMMEDIATE ENROLLMENT-
(i) IN GENERAL.– The school selected in accordance with this paragraph shall immediately enroll the homeless child or youth, even if the child or youth—is unable to produce records normally required for enrollment, such as previous academic records, records of immunization and other required health records, proof of residency, or other documentation;” 42 USC 11432(g)(3)(C).