Chapter 10 Install and System Administration for FortiOS 5.0 : Advanced concepts : Administration for schools : Logging
  
Logging
Turn on all logging - every option in this section should be enabled. This is not where you decide what you are going to log. It is simply defining what the UTM profiles can log.
Logging everything is a way to monitor traffic on the network, see what student’s are utilizing the most, and locate any potential holes in your security plan. As well, keeping this information may help to prove negligence later in necessary.
See Also
Administration for schools
Security policies
DNS
Encrypted traffic (HTTPS)
FTP
UTM security profiles