A lower value indicates smaller class sizes. Andover (thick blue line) has one of the lowest values over the past ten years. Including data for the past ten years and ranking districts based on median student to teacher ratio (the intersection of the two boxes; “whiskers” indicate top and lowest quartile data). In 2019, Andover’s student to teacher ratio (12.7) was the same as Westwood (12.7) and higher only than Wellesley (12.6).