The Board of Education Rev A does not have servo ports. However, 3-pin connections for servos and other devices can be built on the breadboard. For an example of connecting a standard servo to the Board of Education Rev A, see the instructions in the Servo Circuit Connections for Older Boards pdf at www.parallax.com/go/WAM. If you wish to supply a 3-pin device, such as a Parallax Continuous Rotation Servo, with a 6-volt power supply via a breadboard circuit, Parallax carries 4 AA cell battery holder with tinned leads (#753-00001) for this purpose.
To disable power on the Board of Education Rev A, you must disconnect the power supply or battery at its connector.