USGBC's Center for Green Schools has Distance and At-Home Learning Lessons available for free on their website.

Examples of courses/lessons include:
Green Living: Identifying Green Businesses in Your Community (6-8) - FREE
Architectural Wonders (9-12) - FREE
Food Waste Warrior Educator's Resource Guide (3-12) - FREE
Local Living Landscapes (3-5) - FREE
Biodiversity Audit (6-8) - FREE
How Natural Areas Filter Water (6-8) - FREE

Check out these and other resources on the Learning Lab website.