The McKinney-Vento Homeless Assistance Act

The McKinney-Vento Homeless Assistance Act (per Title IX, Part A of the Elementary and Secondary Education Act, as amended by the Every Student Succeeds Act) is a law that protects students and youth experiencing homelessness. The law requires every state to monitor the identification of students facing homelessness and provide the necessary support to reduce the many barriers that prevent students from succeeding in school.

McKinney-Vento Homeless Assistance Act defines homeless as follows:
The term “homeless children and youths”–

• lack a fixed, regular, and adequate nighttime residence and includes—
• children and youths who are sharing the housing of other persons due to loss of housing, economic hardship, or a similar reason; are living in motels, hotels, trailer parks, or camping grounds due to the lack of alternative adequate accommodations; are living in emergency or transitional shelters; or are abandoned in hospitals;
• children and youths who have a primary nighttime residence that is a public or private place not designed for or ordinarily used as a regular sleeping accommodation for human beings (within the meaning of section 103(a)(2)(C)); 
• children and youths who are living in cars, parks, public spaces, abandoned buildings, substandard housing, bus or train stations, or similar settings; and
• migratory children (as such term is defined in section 1309 of the Elementary and Secondary Education Act of 1965) who qualify as homeless for the purposes of this subtitle because the children are living in circumstances described in clauses (i) through (iii).

*Per Title IX, Part A of the Every Student Succeeds Act, “awaiting foster care placement” was removed from the definition of homeless on December 10, 2016; Students living in foster care are now protected under the act.

Source: https://nche.ed.gov/mckinney-vento-definition/

Unaccompanied homeless youth are young people experiencing homelessness who are not in the physical custody of a parent or guardian.