Empirical research increasingly raises doubts concerning the selective school system. The canton of Zurich has responded to these findings with a new school law, according to which all children, including those with special educational needs, should be taught in regular classes. To support the regular teaching staff in creating an adaptive design of lessons, the teaching-related cooperation of regular teachers with specialised teachers becomes increasingly important. However, there is only little empirical evidence about the effects of such cooperation. This master thesis should answer the question of what the teaching-related cooperation between the regular and special teachers is and what relevance this has for successful teaching in heterogeneous learning groups. To answer the question, expert interviews were conducted with twelve groups of regular and special teachers and evaluated by a form of qualitative content analysis. The results show, that teaching-related cooperation between regular and special teachers takes place, but substantially differs. Most regular and special teachers identify lack of time as a major difficulty. Moreover, it appears that fixed cooperation settings for joint lesson planning as well as the sympathy of the cooperation partners represent key conditions for success. Although many respondents indicate that teaching-related collaboration is helpful for dealing with diversity in the classroom, it is not carried out in all schools as an integral part of professional practice. Support in the form of structural framework conditions, team development and addressing of collaboration in the education and training therefore seem to be essential for good teaching-related cooperation and consequently a successful management of heterogeneous learning groups.