A study of the language proficiency of students in core French programs in a number of Eastern Ontario (Canada) high schools looked at the listening comprehension, reading comprehension, and oral skills of students in grades 9, 10, and 12. Comparisons were made across and within school districts, and also with previous groups tested. Findings show clearly that the cumulative amount of French instructional time does influence proficiency, particularly at the grade 9 level. While grade 9 students do not generally score as high on listening tests as late immersion groups with similar amounts of instructional time, by grade 12 the core groups with 1,200 or more hours of French compare favorably in French listening and reading with students who have had two years of a late immersion program with 50 or 80 percent of the time spent in French. The study revealed the need for more appropriate tests and for closer examination of the factors affecting the achievement of second language proficiency. (MSE)