Human issues such as leaving machines logged on when not in use are the major cause of security breaches in schools. Any user can sit down at a logged on station and have the full network rights of the individual whose computer they are using. Students would be able to get to teacher or administrator parts of the network. A system or combination of systems that enforces a boundary between two or more networks.
Firewalls protect one part of a network from another.
They control the type of data, the source of the data, as well as destination of the data as it flows through various network connections. The school determines the business rules that the firewall will use to control the traffic. It will screen out unwanted traffic and allow all other traffic to move about normally. Some schools configure firewalls but create large holes for the outside to get in. For example, some schools allow students to update school websites from home.