A Boy Scout is a boy, usually 11 to 18 years of age, participating in the worlwide Scouting movement. Because of the large age and development span, have many Scouting associations split this age group in a junior and a senior section. Boy Scouts are organized into troops averaging twenty to thirty Scouts under guidance of one or more Scout leaders. Troops subdivide into patrols of about six Scouts and engage in outdoor and special interest activities. Troops may affiliate with local, national and international organizations. Some national Scouting associations have special interest programs such as Air Scouts, Sea Scouts, outdoor high adventure, Scouting bands and rider scouts. Some troops, especially in Europe, have been co-educational since the 1970s, allowing boys and girls to work together as Scouts.