There's no single average class size for Louisiana State University (LSU). The average class size varies significantly depending on the course, department, level (undergraduate vs. graduate), and even the instructor. Some courses, especially introductory large lectures, can have hundreds of students, while others, particularly upper-level seminars or graduate courses, may have only a dozen or fewer.
To find a more specific answer, you'd need to look at data from LSU directly, perhaps in their institutional research office's reports or publications. Even then, you'd likely find ranges or averages broken down by various factors rather than a single overall average.