An arts-based supplemental education program was evaluated qualitatively and quantitatively. It was hypothesized that this classroom program would cause gains in critical thinking skills, as measured through writing ability. The program provided 87 teachers in grades 3 through 12 with a classroom set of "Arts Indiana" magazine and an accompanying study guide. The qualitative study of teacher use of the resources and materials of the program identified teachers who were using the program effectively. About half of the program teachers agreed to participate in the quantitative part of the study, designed to evaluate students' critical thinking and writing skills. This study was completed in the context of a new state high school achievement test of writing. About 2,000 pretests were obtained after summer vacation before students participated in the supplemental program and about 1,700 posttests of student writing were also completed. Classwide losses in critical thinking skills were actually seen from pretest to posttest. Although the supplemental resource did not cause greater gains in critical thinking among its users, its effective use did reduce the classwide losses in students' critical thinking and writing experienced between the pretest and the posttest. Implications for teaching in general and for this program in particular are discussed. (Contains seven graphs.) (SLD)