The testing of the ECO-COMPASS innovative environmental education materials in easy-to-understand language took place from June to August 2023.Each of the three partner countries joined the testing, attended by 32 participants. In Slovakia, the testing was implemented by the Association helping Mentally Disabled People in Dunajska Streda, while in Romania, it was implemented by the Iris House in Sfantu Georghe. In Hungary, testing took place at "Erdőszéli Lélekfarm" ("Forest Eave Soul Farm"). Trainers assessed the content of training material (the videos, theoretical part, the questions, the exercise sheets, the quiz, the outdoor tasks), the applicability, the atmosphere of the meeting as well as the online platform with the maximal score. The skills of the mentally disabled people improved during the training. They learnt to apply the skills they acquired in their everyday life, within the family and at work as well. They are also glad to join any social activity, the aim of which is to protect our environment.