Effects of an advance organizer lesson (containing high-order science concepts relating to the law of capillary attraction, and an elementary problem-solving strategy for determining causal relations) were evaluated for a sample of 80 urban 6- and 10-year-old children. Significant sequential transfer effects were established from the lesson. Improved performance for experimental groups was maintained on a retention test and transferred to a second problem in that class of problems involving operations of exclusion. There was a marked tendency for performance to improve with age. Results suggest that acceptable solutions to problems requiring the operations of exclusion may be achieved without the use of complex propositional logic. (Author/MS)