Need help finding the correct chair sizes and table sizes for your students? The school chair sizes usually go by grades. The chair size for preschool and smaller kindergarteners are generally 12″ chairs. Larger kindergarteners, most 1st graders, and smaller 2nd graders will use a 14″ chairs. Larger 2nd, most 3rd, and 4th grade students will use a 16″ chair. The 18″ chairs fit the tallest 5th graders and are mostly used for middle schools, high schools and colleges. The following is a helpful chart for correct chair and table sizes for each grade.