Former pupils, teachers, and other members of the school are known as Old Southendians, and are entitled to join the Old Southendian Association (OSA) of past members and alumni, to keep in touch and network with other former pupils at social, sporting, and musical events, and on trips and meals. The OSA has the motto "sustaining friendships", and is one of the oldest and largest Boys Associations in the country, with 2,470 members as of October 2011. The school also has a Parents' Association (PA), which is a registered charity, and associated PA Committee.