WebScreen is a highly flexible web filtering system designed and built for the UK education sector, fulfilling the requirement of the Department for Education’s statutory safeguarding guidance ‘Keeping Children Safe in Education’ to offer 'appropriate filtering'. Its user manual is online at https://webscreen.lgfl.org.uk/UserManual/index.html
This system is capable of decrypting your 'https' traffic for monitoring and filtering purposes. The system administrators can be seen as attackers of your privacy. They'll be in the middle of you and your internet traffic, they can journal your use, they cannot see the browsers' history. They'll see the passwords once you use them, not your password store.
Using the certificate only in Firefox, not system-wide, is recommended.