The answer depends on the type of grass you have and your region of the country. Cool season athletic turf (bluegrass, ryegrass, and tall fescue) should be mowed at a height between 1 ½” and 2 ½.” Many schools feel that longer is better and keep the heights of 3” plus. On the contrary, cool season grasses develop much denser root systems at lower heights – down to about 1 ½” (depending upon the species and varieties selected). The downside of shorter grass is that divots are more visible and shorter grass must be mowed more frequently.