Support Our Schools Act This bill provides additional FY2021 funding for the Department of Education to address the continued impact of COVID-19 (i.e., coronavirus disease 2019) on elementary and secondary schools and institutions of higher education (IHEs). It also provides additional FY2021 funding for specified purposes to the National Endowment for the Arts, the National Endowment for the Humanities, the Institute of Museum and Library Services, and the Administration for Native Americans. In addition, the bill modifies the so-called 90/10 rule to require for-profit IHEs to include all forms of federal education aid in the revenue calculation for federal student-aid program eligibility. (Generally, this rule requires a for-profit IHE to derive at least 10% of its revenue from sources other than federal financial aid.)