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Web Filtering Solutions: What Schools, Colleges and MATs Need to Know

6 minute read
By Smoothwall

According to both KCSIE and Ofsted, web filtering is an essential safeguarding function - a school cannot fulfil its safeguarding duties without having an appropriate filter in place. This article covers the different types of filters often used within UK education, and the factors to consider when selecting a vendor.

Who is responsible for web filtering in UK schools?

In line with the Department for Education’s filtering standards, establishing and employing a filtering system within a school requires input from leadership, IT staff and DSLs. However, it is the IT staff and/or service providers who shoulder the majority of responsibilities. Their remit includes:

  • Procuring and maintaining filtering systems
  • Performing reviews and checks
  • Providing filtering reports
  • Responding to concerns or faults with the system
  • Performing reviews and checks (The DfE suggest that this should be done annually)

What does a school web filter need to do?

KCSIE outlines that a good web filtering system should strike a balance between protecting children from harmful content and allowing them to enjoy a productive online learning experience. 

This view is supported by Ofsted, who identified as far back as 2010 that “pupils were more vulnerable overall when schools used locked down systems because they were not given enough opportunities to learn how to assess and manage risk for themselves.” 

To navigate today’s online landscape, a filter needs to be able to track and decipher a variety of content that is continually updating, evolving and proliferating. While no web filter can guarantee 100% protection against online threats, deploying the right filtering technology for your school can help mitigate the vast majority of risks students face online.


What types of web filters are used within schools?

There are 4 main types of filter currently utilised within UK education. They vary in their level of protection and, to some degree, the level of maintenance required from IT staff to keep students safe. What works best for a certain school will depend on their specific requirements, preferences and budget. 

DNS filters

DNS filters restrict content on the basis of domain names. As they cannot distinguish between different pages or types of content on a site, a DNS filter relies on a list of banned domains. When a person types something into a browser, for example, the filter checks whether the domain matches any websites on the blocklist, and acts accordingly. 

Overall, this is a broad approach to filtering that often results in both overblocking, where a filter restricts access to non-harmful pages that could be useful in an educational context (for example, certain videos on YouTube), and underblocking (in the case of search engines like Google Images). 

Pros: Can be very easy to deploy; cheaper than other filter types; better than no filtering.

Cons: Cannot meet UK SIC standards; high exposure to risk remains; blocklists can take months to update and require constant maintenance and input from IT; overblocking/underblocking likely. 

URL filters

URL filters restrict specific pages of a website, rather than blanket blocking an entire site. For example, certain pages on the BBC website may be accessible, but those relating to violent or disturbing news stories could be blocked. In this way, URL filters are slightly better at capturing the search intent behind what a user is trying to access. 

A downside of URL filters is that they rely on fairly static blocklists. As a result, they are not equipped to categorise new or rapidly changing content. This means that if a previously approved web page is updated to include harmful content, it could remain unfiltered for some time before being flagged. 

Pros: Blocks pages rather than entire sites; better at capturing search intent than DNS filters.

Cons: Struggle to deal with new or changing content; exposure to risk still high; overblocking/underblocking can occur.

Content-aware filters

Content-aware filters can interpret the actual content on a page and use this information to inform whether to restrict it or not. This is a more sophisticated approach than simply comparing the URL to a list of websites or web pages. 

Keep in mind, though, that many content-aware filters only analyse small portions of online content, so unfiltered grey areas may still exist between a search and a destination site. 

Furthermore, filtering is based on a historical assessment of a site. As a result, harmful content that only recently appeared on a page may evade detection. 

Pros: Able to analyse on-page content; more sophisticated than DNS and URL filters; reduces instances of overblocking/underblocking. 

Cons: Partial exposure to risk remains; may only analyse small portions of content; decisions based on historical assessments so not as effective at analysing new content or pages.

Real-time, content-aware filters

Real-time, content-aware filters harness the power of content-aware filtering and combine it with the capacity to analyse content in real-time. As users explore the internet, every web page is assessed for content, context and construction. This dynamic approach significantly reduces overblocking and ensures that there is no delay between harmful content going live and the filter taking appropriate action.  

These filters offer the highest level of safety, whilst also ensuring that students can achieve a rich online learning experience. For example, pupils working on a project about Henry VIII may want to view web pages that include the word “behead”. A real-time, content-aware filter would register the intent behind such searches and allow access to educational web pages covering Tudor history. 

Students can also benefit from safe access to useful social media platforms and online communities, such as Facebook and Reddit. The nuanced approach of these powerful filters means that potentially dangerous content found within these sites is blocked, while content and pages relevant to learning remain accessible.  

Pros: Most sophisticated filter type on the market; exposure to risk is minimal; even new and updated content is analysed; overblocking/underblocking significantly reduced; more future-proof to changes online than other filters.

Cons: Higher price point than basic filters.

What should I look for when comparing filter options? 

The Filter Safety Pyramid 

Whether you’re assessing your current system or comparing available options, our Filter Safety Pyramid can help IT Leaders identify which filtering solutions are fit for purpose. 

Filter pyramid


In an educational setting, filtering should sit in the ‘safety zone’ at the top of the Filter Safety Pyramid to meet the ‘appropriate’ level of safety outlined in KCSIE 2023 statutory guidance.

Deployment options 

When choosing a filter, schools should also consider how the system will be deployed. The options available at this stage will depend on the selected vendor. Smoothwall Filter, for example, provides ITs with a choice of on-premise, cloud or hybrid deployment.

Multi-academy trusts may also want to ensure that web filtering solutions allow for scalability and standardisation

100% real-time, content-aware filtering for schools

A content-aware web filter that assesses every aspect of a page in real-time is the only filtering solution that falls in the safety zone of the Filter Safety Pyramid. 

With this solution, even harmful content that is seconds old can be assessed and restricted so that students are provided the best level of protection. At the same time, they allow a vast variety of sites to be made at least partially-accessible, empowering students to embark on a fruitful online learning journey.

Learn about real-time content filtering with Smoothwall

Discover how Smoothwall Filter can help ensure your system sits at the top of the Filter Safety Pyramid, whilst exceeding appropriate filtering standards set out by KCSIE and DfE.

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