The purpose of the present study was to broaden planned behavior theory and examine its applicability to predict the academic achievement of students of low and high spelling ability. Two hundred fifty seven students, 54 low spellers and 203 high spellers from thirty elementary schools in northern Greece, participated in the study. Between groups comparisons pointed out differences in attitudes and motivation: low spellers had significantly lower "goal importance," "intent to achieve," "belief strength," "outcome evaluation," "motivation to comply," and, language and mathematics achievement. A simultaneous evaluation of the contribution of goal importance as an antecedent of attitudes, intentions, and normative beliefs was supported using Structural Equation Modeling (SEM). However, differential--between group--construct relations suggested the presence of different regulatory systems.