Desegregated schools have not been found to significantly affect racial attitudes. In schools, races tend to associate with their own members. Classrooms and many other settings are often arranged on a competitive basis. The invasion of the Falkland islands. Sherif had the water supply break down, and the truck got stuck - both groups cooperated, and eventually became good friends.
Successful cooperation decreases conflict - but unsuccessful cooperation can increase it.
You blame the other group. Children assigned to racially and academically diverse 6-member groups. Material divided into 6 parts, each student becomes expert in their area, and has to teach their classmates. Also, cross-racial friendships blossom, exam scores of minorities improve. In many situations, influence is bilateral rather than unilateral.