This toolkit has been developed by the American University of Armenia (AUA) in the frame of the EU-funded OTTERS (Social Transformation for Water Stewardship through Scaling Up Citizen Science) project with the active engagement of AUA students. The resource aims to provide school teachers and educators with guidelines on how to integrate citizen science elements as project-based learning in their curricula, by providing background knowledge of eutrophication with the example of the Lake Sevan ecosystem in Armenia and step-by-step instructions on measuring and reporting water quality parameters.