[kintamanimatt]

What kind of site are they running?

[ColinWright]

The ones I work with are math sites - one example is http://nrich.maths.org/frontpage, another is http://www.samholloway.co.uk/.

Here: https://pbs.twimg.com/media/BcME5NvCAAAeslD.png

I'm also told that Boots, CEOP, Childline, HM Govt, NHS, Police, and Samaritans sites are blocked, although I don't have first-hand confirmation.

[kintamanimatt]

Math sites are blocked as unsuitable for kids?!! That's utterly absurd. The British government needs to abandon this puritan initiative.

[desas]

That screenshot says it's blocked on the opt in under12 filter, that's been running for years. It's a whitelist, those sites have probably always been blocked on it.