The main and interactive effects of classroom openness on the achievement and creativity of 103 third graders and 97 fourth graders were assessed by multiple regression analyses. After controlling for student IQ, socioeconomic status, sex, age, anxiety and "family openness," classroom openness was found to be negatively related to achievement and creativity measures at both grade levels. However, the increments in explained variance attributable to classroom openness were consistently significant for the fourth grade only. Two student characteristic X classroom openness interactions were found, each of which affected verbal creativity. Further attention to IQ X classroom structure interactions is suggested in this paper. (Author/WI)