This work explores whether a "psychological price" is indicated in the affective domain of the weaker student in abilty-mixed settings; whether this price differs for various dimensions of this domain; and whether it is related to academic achievement. Existing research in the fields of ability grouping, streaming, curriculum tracking, and ethnic segregation and integration is analyzed and supplemented by an in-depth study of two Israeli samples. A major finding is that the level of classroom intellectual composition is negatively related to evaluations of learning motivation and academic self-image but positively related to sense of control (and sometimes to aspirations), and analogously related to the positive effect of classroom composition on academic achievement. It is suggested that different socio-psychological processes may affect achievement and certain affective variables differently than they do other affective variables. In the cognitive domain, and possibly in the case of control and aspirations, the class is more likely to function as a norm resource. In contrast, comparative reference seems to be more effective in influencing self-image. It is concluded that even if enrichment of intellectual composition involves the psychological price of a lower academic self-image and reduced motivation for the "lows," their academic achievement is not reduced but increased. (Author/RDN)