Web filtering in schools

Web filtering in schools blocks students from inappropriate content across the web, while allowing sites that are selected by school administrators. Rather than simply blocking off large portions of the Internet, many schools are utilizing customizable web filtering systems that provide them with greater control over which sites are allowed and which are blocked. Schools will typically block NSFW content, social media websites, games, distracting websites, websites that harm academic integrity etc.
By region
United States
The Children's Internet Protection Act (CIPA) requires that U.S. schools have appropriate measures in place to protect students from obscene or harmful online content in order to be eligible for discounts on internet access or internal connections through the Schools and Libraries Program of the Universal Service Fund, commonly known as the E-Rate program. There are a number of commercially available free and paid services that allow schools to meet CIPA requirements and receive the discount.
Other countries
These practices exist in Australia, the United Kingdom, New Zealand and Canada, among others. Such filtering blocks Netflix, YouTube, Facebook, Twitter, Instagram, certain games and more.
Types
The FCC and CIPA do not specify how the filtering needs to be done, so most schools are using a combination of DNS, browser and firewall-based filtering.
DNS filtering
The DNS filtering happens at the domain resolution layer of the Internet and does not allow the IP address of an obscene or harmful website to be discovered. There are multiple paid products that perform such work, but many schools are leveraging free solutions to filter non-safe sites.
Browser filtering
Some browser extensions allow parental controls to be enabled to restrict non-desirable website categories. For CIPA, those categories include any website with adult-only content.
Firewall-based filtering
Firewall-based filtering can be done at the IP layer or using Web proxies to intercept and filter HTTP and HTTPS requests to websites that are not kid-safe. This type of solution is difficult to implement as much of the web is moving to HTTPS, so it does not have a high efficiency.
SafeSearch filtering
Google SafeSearch helps filter out explicit adult material from Google Search results and can be enabled by default in schools.
Teacher Classroom Management
Some schools also have tools which let teachers control their students devices including the blocking or unblocking of certain websites during for that class or class period.
Blocking Schedules
Some filtering software may allow schools to allow students to have less restricted access during certain times. For example some schools may allow some social media or game usage outside of school hours, if students are allowed to take their devices home. Although most schools strongly encourage their students to keep their school issued devices for academic purposes only and use their personal devices at home for social media and video games.
Bypassing
Some web filters have the ability for teachers to login and bypass web filters usually for an hour. Some school districts turn this feature off or have a list of websites that are still blocked even if the filter is bypassed.
Some students also try to get around filters themselves, but this can result in loss of device or suspension from school. Most schools require their students to sign contracts to receive their device at the start of each school year, these contracts usually prohibits the students from tampering with the filtering/security software.
See also
Don't Filter Me
References
Internet safety
Child safety
Cyberbullying
Internet censorship in the United States
Internet censorship
Educational technology