School is an educational institution where students acquire knowledge, develop various abilities and skills, and acquire habits, but also accept certain values and universal and social norms. A student's development requires nurturing and developing relationships with other students, particularly with those with a certain difference, i.e., distinctiveness. Inclusive education, which is based on tolerance, promotion, acceptance, and respect for differences and their inclusion, comes as an answer to discrimination, violations of rights, prejudices, and the exclusion of those who are different. The basic aim of inclusive education is to encourage the development of all students and their potential while at the same time respecting their developmental and educational potential, abilities, and special needs. The teacher's role in the concept of inclusive education is rather demanding. For the successful implementation of inclusive education in regular schools, teachers need support. One of the forms of support for teachers is assistance, i.e., the participation of assistants in teaching students with developmental difficulties. Namely, teaching assistants exemplify a bridge connecting the teacher and student with developmental difficulties in overcoming obstacles during the educational process. However, successful inclusion does not only imply quality cooperation between the teacher and the teaching assistant but also with the parents of students with developmental difficulties. Together, they create a triangle of inclusive support for students with developmental difficulties, while quality and constructive cooperation, communication, and partnership between them also contribute to the quality of the implementation of inclusive education. The paper examines the assessments of teachers, teaching assistants, and parents of students with disabilities on cooperation, as well as the existence of statistically significant differences in their assessments.