Lessons about elementary particles at the secondary school level can degenerate into listing a zoo of particles and reactions, resulting in disorganized and rather meaningless knowledge. A more powerful way is to focus on conservation laws, symmetries and reaction diagrams. The conservation laws and symmetries provide generalizing power that enables the students to predict whether or not certain reactions are possible and to derive new reactions from given ones by applying the symmetries. In this article we first present simplified Feynman diagrams and three symmetry operations. Then we discuss the fast feedback teaching method and present two lessons and a worksheet for teaching symmetries and reactions using this fast feedback. The method was developed and piloted during the last two school years in Dutch secondary schools.