[AstralStorm]

The market is there, schools would love this technology. The problem is that simple thin coat of aluminized paint is super expensive, as is a big mesh. And phones are very effective at getting the low signals through any available hole in filter coverage.

[JPLeRouzic]

I wonder if it would be possible to install a 4G network extender [0] then implement IP route rules on the ADSL router, to forbid access to Facebook and co?

[0] https://www.verizon.com/support/4g-lte-network-extender-faqs...

[rosswilson]

Those extenders typically backhaul the traffic over a VPN back to the telco, so your router would never see the true destination (e.g. Facebook).

[cskinner]

And will ramp their transmit power up to do so.