Geo-boards can be used to teach mathematics from kindergarten through 9th grade. They are particularly useful for teaching geometry, graphing, and other topics to students from 1st through 3rd year of secondary school. The document outlines specific curriculum topics that can be covered at each grade level using geo-boards, including shapes, fractions, trigonometry, and more. It provides contact information for a teacher who can visit schools to teach math lessons with geo-boards free of charge.