I'm not suggesting that there should be no "filtering" of adults, I totally agree that there is a whole plethora of sites that should be "blocked" for the many and various reasons that we all know. Of course everybody's internet in school should be filtered. In addition to those that should rightly (or wrongly sometimes), be blocked by default, I now have access to a portal where I can custom block/unblock. ( I've never had that before. Previously I had to fill in an e-form and my request was validated by the filtering provider and then enacted. I'm not actually sure I want to be solo accountable for blocking/unblocking directly - as you say, too much responsibility. I know some small schools that will just unblock if a lesson has been prepared without considering anything or website T'S and C's or privacy policies, the Data Protection Act - just for expediency, I also recall the KS1 teacher that asked the class to search for "Asian Bears" when filtering was less capable than it is now. but I digress...)
My concern is of covert surveillance of adults by the Local Authority, the exposure of Account ID's, passwords, credit card, "sensitive personal data" etc as defined by the DPA/GDPR and and also that of third parties from social media updates on BYOD devices by decryption of HTTPS, and what the legal basis is that is being relied on for doing this.
Decryption is not needed to block access to HTTPS.