Both federal and state guidance provides that students with individualized educational plans (“IEPs”) may be entitled to compensatory education during school closures to make up for any skills that may have been lost. 
Whether and to what extent compensatory services are owed must be made on an individual basis. The California Department of Education, provides that “educational need can be measured by assessing whether or not the student made progress in the general education curriculum, or in the alternative course of study specified in their IEP, or toward meeting their individualized IEP goals, and/or if any regression occurred during the period of the school site closure.”
There is no formula to calculate the how much compensatory services a student would be entitled to. However, it would be important to document whether and how much services are being provided during the school closures. To assist with this, attached is a weekly log template that can help you track the services and instructional times your child is (or is not) receiving.
 https://www2.ed.gov/about/offices/list/ocr/docs/ocr-coronavirus-fact-sheet.pdf United States Department of Education March 16, 2020 Fact Sheet: Addressing the Risk of COVID-19 in Schools While Protecting the Civil Rights of Students
 https://www.cde.ca.gov/ls/he/hn/specialedcovid19guidance.asp California Department of Education Special Education Guidance for COVID-19