With the advent of relatively large classes of students studying arithmetic in common schools, educators began to prepare special charts to assist in instruction. By 1900, these could be quite extensive. Arithmetic charts, like textbooks and flash cards, reflected contemporary ideas. Charts made in the 1830s were designed specifically to be used with a numeral frame. Those made in the 1890s showed metric as well as standard weights and measures. A chart from roughly the era of the New Math showed a number line—a mathematical construct not previously taught to young schoolchildren.