This resource from the NAACP, Teaching Intersectionality and Environmental Justice in Our Classrooms, is a good starting point. It provides a critical intersectional framework for the examination of environmental justice and contains a resource list for websites such as the National Institutes for Environmental Health Sciences and the Center for Ecogenics and Environmental Health, among others. It also includes links to lesson plans and videos.
Future Learn provides full courses on climate change (not specifically EJ) developed by Universities from around the world. Some courses are free, but there may be fees related to specific course content. Depending on the subject or course you can get free access for a limited amount of time usually longer than 6 weeks. Note, this is most appropriate for OY participants.