Intercom systems are fairly complex, although it does depend on how much functionality the school wants from its system. At the very least, there should be a two-way paging system, where a central office can page any specific room or area of the school, and the teachers in those areas can communicate back. An emergency broadcast system may be included that allows anyone from an intercom to broadcast to the entire school. Some schools will integrate inputs for music or microphones so that the speakers installed in a classroom can do double duty. These systems require hard-wiring throughout the school, which does make installing a system during a build or renovation easier than upgrading the system alone.
A PA system for a school's athletic announcers is a very helpful thing to have, although smaller schools may choose not to undertake the expense. If the school has teams that compete outdoors as well as indoors, such as football or soccer teams along with their basketball and volleyball squads, then a portable PA system can work well. Major schools that have well known and highly funded football programs have larger stadiums, and usually have a dedicated PA for calling the football game, and another, smaller system for working on indoor sports.
If assemblies take place in an auditorium or theater space, then the same sound system can be used that is used for other productions that take place in the space. If not, a separate assembly PA system will be required. This system does not need to be complex if it is a stand-alone system for a gymnasium, for example. A simple PA amp, speakers and microphone can suffice. Amps should supply phantom power so that a wider variety of microphones can be operated, and they should include several microphone inputs to accommodate multiple speakers.
Theater sound systems have two basic requirements. There must be a means of playing music, and a method for amplifying performers on stage if needed. A mixer, amplifier, speaker system and several input devices are required. A CD player was most often used in the past to play music, but systems have transitioned to a laptop computer connected to the mixer to run the sound for shows. A large number of auxiliary and microphone inputs are required. A wide selection of mics should be present, including ribbons, wireless lavaliers, dynamic and condenser microphones.