This study investigated the effects of the addition of a supplemental science program to existing curricula in selected elementary schools. A supplemental science program, the Elementary Science Study (ESS), was introduced to the treatment group (four of eight classes randomly selected, with a total population of 189 sixth-grade students) and a placebo treatment consisting of films, current events, and discussions was given to the control group for one hour a week, during a twelve week period. The Stanford Achievement Test, The Home Index Scale and The Reed Science Activities Inventory were administered at the end of the study. Analysis of the data was accomplished using factorial 2 x 2 analysis of variance on each of the four variables. It was found that the supplemental science program made a difference in science achievement favoring the experimental group. Non-Indian students scored higher in science achievement. Students with a high socio-economic background did better than did those with a low socio-economic background. The effect of science attitude on achievement was non-significant. (Author/EB)