This report describes research into the effectiveness of the language laboratory in improving students' reading, listening and speaking skills in secondary school language programs. The experiment, involving some 5,000 students in 21 school districts of the Metropolitan School Study Council, was restricted to students of French. Student achievement of the laboratory and the non-laboratory groups was based on various examinations: (1) a speech production test, devised for the experiment and administered to a 10 percent sample; (2) The Cooperative French Test (Series Q) measuring reading comprehension skills; and (3) the Cooperative French Listening Comprehension Test (Form B). Experimental design relies heavily on classification of students by intelligence quotient scores. Generalizations drawn from the results reflect the difficulty of objective experimentation and the limitation of this study, referred to in a special section. Statistical data are included in an appendix. (RL)