William Lau, Head of Computing at Greenwich Free School, explores the importance of asking fertile questions when building lessons

When I first arrived at Greenwich Free School in August 2013, there was no existing ICT or computing curriculum. The national curriculum for ICT was being reformed and the new computing curriculum was still in draft. Therefore, I had to write my own curriculum from scratch and initially I managed by writing lessons a week at a time.

Eventually, I devised a curriculum map based on several key areas of the OCR GCSE Computing specification.  Initially, many of the lessons were adapted from CAS resources, then over time, I would also publish my own lesson resources and meet many of the teachers and professionals in the wonderful CAS network.

Thinking like a Computer Scientist

Looking back, whilst the initial curriculum I designed was exciting- students learnt about upgrading their PC and making a website to showcase their work - my students were not necessarily thinking like computer scientists.

A new head teacher, Oli Knight, arrived at the school and instilled the notion of developing expert thinking in our students for our respective subjects. He asked us to think about what it meant to be an expert computer scientist or an expert IT user. He also introduced middle leaders to the concept of fertile questions.

Fertile Questions

Fertile Questions are a way of encouraging understanding rather than mere recall. For many years the focus has been on producing the ‘correct answer’. This can however lead to a culture of rote learning, where mistakes, errors and misconceptions are avoided and hidden by the learners rather than embraced by the teacher and corrected. A fertile question on the other hand has six attributes:

Open: A question that does not have one definite answer but rather several different answers which may even contradict each other.

Undermining: A question that undermines the basic assumptions and fixed beliefs of learners. This may challenge common sense and lead to conflicts which lack simple solutions.

Rich: A question that requires grappling with rich content indispensable to understanding humanity and the world, that is impossible to answer without careful and lengthy research. This question may break up into sub questions.

Connected: A question relevant to the learner’s lives, society and to the discipline and subject within which it was asked.

Charged: A question with an ethical and emotional charge able to motivate learning and inquiry.

Practical: A question that can be developed into a research question; a question about which information is available to students.

Teaching towards Computer Science GCSE

As a school, we developed our own five year curriculum maps which mapped backwards from the GCSE, with the aim of developing junior experts in Computer Science and IT.

Fertile questions are embedded in each unit and referred to throughout the unit’s lessons. I’ve noticed that this has helped students gain a much deeper level of thinking. Their maturity and ability to think more like expert computer scientists and IT users is evident in the questions that my students ask.

In 2013, my students would ask trivial questions such as: ‘Which is better, an XBOX One or a Playstation 4?’

Four years later, these same students are now studying GCSE computer science, over 40% of them are girls and these are the questions they have recently asked:

  • If MAC addresses are unique but they can be spoofed, what happens if you spoof your MAC address to an address that already exists?
  • If Python is written in CPython, what is CPython written in?
  • If you run out of RAM, we rely on virtual memory. So, what happens if you run out of virtual memory?
  • How can Netflix detect if you're using a VPN?
  • What happens to a data packet if you shut down your computer?
  • If you do a binary search and there's an even number of elements, which element do you choose as the middle for the pivot?
  • How does a random module generate a random number? Is it actually random?

Expert thinkers

It is clear that these students have moved beyond the trivial thinking of a novice and have now moved onto more expert thinking. It’s been an amazing journey transitioning from an ICT teacher to a CAS Master Teacher and Head of Department and I hope to continue to share what I’ve learnt through my writing, CAS workshops and events.


  • Harpaz, Y., 2005. Teaching and Learning in a Community of Thinking. Journal of Curriculum and Supervision, 20(2), pp. 136-157.
  • Lau, W., 2017. Teaching Computing in Secondary Schools. Abingdon: Routledge.
  • Six Basic Characteristics of a Fertile Question adapted from Harpaz (2005)

About the author

Supporting the government’s ‘Digital by Default’ strategy we’re keen everyone has the skills and confidence to use IT. Here, we share thoughts on a variety of digital matters.