I believe that I am the only primary school in Torbay, Devon not on the SWGFL, this is through choice and my extensive experience of working in education, mainly in secondary in various role in educational ICT.
I chose to not use the SWGFL for a number of reasons and experiences that I have had using it and non-SWGFL ISPs.
Cost - the SWGFL is EXPENSIVE for what you get
Reliability - over the years that I used it I found it to be unreliable
Port assignment and filtering - Paper chase to get any ports open and filtering is a pain.
RM Cheesy-Mail (oh sorry....... Easy Mail) - Not good.
Virus infection - approx 4 years ago whole of SWGFL was hit by blaster.
I have an 8MB ADSL Business connection with Eclipse that costs £54 a month with hosting, for filering I have a RM Smart Cache II box with RM Safety-Net (which I must say I find to be very good - despite what others are saying on this forum), this also runs Espresso.
Downside of not using SWGFL if anyone is interested:
Cannot access parts of the Torbay Portal (no loss there then!)
ScoMIS cannot provide remote support.
Attix Backup problem (ScoMIS looking into as I write this).
Upside:
Total Firewall control - have been able to set up VPN, Moodle, FTP etc etc with no fuss.
Fast, reliable connection.
Decent webmail and POP3 access.
Total filtering control.