Teaching science through big questions and big ideas

The GCSE science specifications are content-heavy in a way that has consequences. There is a lot to get through, the assessment objectives pull in different directions, and the path of least resistance for any teacher under pressure is to march through the specification topic by topic, ticking each off as you go. The students survive, the grades come in roughly where you expected, and at the end of two years they often cannot tell you what science is actually about.

The 'big ideas' framing offers a counterweight. It suggests that the disparate specification content (cells, atoms, forces, ecosystems, electricity, evolution) hangs off a small number of foundational ideas, and that students learn the specification better when they can see those ideas threading through everything. It is not a replacement for the specification. It is a way of organising the specification so it makes sense as science rather than as a list of facts.

This guide is aimed at science teachers and HoDs who want to bring more coherence to their KS3 and KS4 teaching without sacrificing the content their students need for the exam. It draws on Wynne Harlen's 'Principles and Big Ideas of Science Education' (the source most ASE-aligned curricula return to), and on the practical work of teachers who have tried to make this approach travel in real classrooms.

Big ideas are not topics. A topic is 'cells' or 'electricity'. A big idea is something more like 'all matter is made of particles that interact in lawful ways' or 'energy can be transferred between stores but is conserved overall'. Big ideas explain what is going on across many topics, and they are the things you would want students to still believe in five years after the exam.

The Harlen ten, in rough form, are: All material in the universe is made of very small particles; objects can affect other objects at a distance; changing the movement of an object requires a net force to be acting on it; the total amount of energy in the universe is always the same but energy can be transformed when things change or are made to happen (Harlen's original wording; the energy-store framing comes from the post-2014 AQA physics curriculum, not Harlen); the composition of the Earth and its atmosphere and the processes occurring within them shape the Earth's surface and its climate; the solar system is a very small part of one of millions of galaxies in the universe; organisms are organised on a cellular basis and have a limited life span; organisms require a supply of energy and materials for which they often depend on, or compete with, other organisms; genetic information is passed down from one generation of organisms to another; and the diversity of organisms, living and extinct, is the result of evolution.

There are other valid frameworks (the AAAS benchmarks, the Next Generation Science Standards in the US, the SCORE Big Ideas for the new National Curriculum work in the UK). The point is not which particular list you adopt. The point is that you adopt one, name it explicitly, and let it shape the way you teach the specification.

Big ideas are the destination. Big questions are usually the route. A big question is the kind of question a curious teenager might genuinely want answered: Why does the moon stay up? Why do we look like our parents but not exactly? How does my phone know where it is? Why is the sea salty? Where does the energy in my food come from? Each one connects to specification content, but it starts somewhere a student can hold on to.

The ASE (Association for Science Education) has been arguing for years that science taught this way (through inquiry into questions worth asking) tends to produce stronger long-term understanding and stronger engagement. The evidence is mostly small-scale and not entirely settled, but the direction of travel in the research literature is that organising teaching around big questions, with the specification content as the substance you use to answer them, beats marching through the textbook chapter by chapter.

The practical move is to start units with a question rather than a heading. A Year 8 unit on respiration that opens with 'Where does the energy in your breakfast end up?' tends to land differently from one that opens with 'Today we are starting respiration. Page 42.' The content covered is the same. The frame around it changes how students hold it.

Big ideas describe what science has worked out. Working scientifically describes how science works it out. The National Curriculum and the GCSE specifications both make the second strand explicit (planning, observing, recording, analysing, evaluating, communicating), and most science teachers nod at it. In practice it often drifts to the margins, particularly when content pressure is high. The required practicals get done, but the disciplinary thinking they were meant to develop is left implicit.

A curriculum organised around big ideas tends to find working scientifically easier to take seriously, because the practicals are no longer isolated tasks; they are the way a particular big idea is being investigated. A required practical on rates of reaction, in this framing, is not just 'do the required practical so we can answer the exam question on it'. It is one of the moves a chemist makes to investigate how particles interact. The student does the same practical, but they are doing it as a chemist, not as a candidate.

This is the part of the change that takes the longest. Building students who can plan an investigation, draw a graph that actually says something, and evaluate the conclusion they reached, requires the habit being built across years rather than crammed before the exam. Departments that take working scientifically seriously from Year 7 tend to see the payoff in extended response questions at GCSE, where students can structure an answer because they have structured many investigations.

One way to make the big ideas useful, rather than abstract, is to map them against the topics in the specification you actually teach. The table below shows a partial example for three of the Harlen big ideas. It is not meant to be exhaustive; it is meant to show what the mapping looks like in practice.

Doing this exercise as a department, even roughly, has two benefits. It exposes where the big ideas land in your specification, and it exposes where they do not. It also tends to expose where a topic has been taught in isolation that could have been more powerful as a return to an idea introduced earlier. Year 11 students writing about photosynthesis are not encountering 'energy is conserved' for the first time. They are picking up an idea they first met in Year 7 and have been refining for five years.

If big ideas are the spine and big questions are the route, the practical work of unit sequencing becomes a bit more legible. Each unit can be framed around a question. The lessons within the unit chip away at that question using the specification content. The unit ends with students articulating their answer to the question in a way that uses the science they have just learned.

A Year 9 chemistry unit on chemical changes, for instance, might open with 'Why does iron rust but gold doesn't?' By the end, students should be able to answer that question with reference to the reactivity series, electron transfer, and the conditions that drive corrosion. The specification content is the same as it would be in any other framing. The unit, as a thing students remember, hangs together because there is a question being answered.

It is worth being honest about the limits of this. Not every unit fits neatly under a single big question, and forcing one usually feels contrived. Some content is foundational rather than question-led, and that is fine. A reasonable goal is that across each year, the majority of units sit under genuine questions, with a handful left in their original form.

Assessment is where this approach often breaks down in practice. The exam papers test specification content in fairly specific ways, and a curriculum that has spent two years on big questions has to still deliver students who can write an effective four-mark answer about the structure of a leaf. The two are not really in tension, but they need to be kept in balance.

In practice that usually means three layers of assessment. Routine retrieval (low-stakes quizzes on specification content), end-of-unit assessments that test the topic in something close to the exam style, and synoptic assessments at the end of the year that test whether students can apply the big idea across topics they have not been pre-prepared for. The synoptic piece is what tells you whether the curriculum is doing what the framing promises; without it, you can be teaching beautifully and producing students whose understanding still falls apart on cross-topic questions.

It also helps to be explicit, in classroom conversation and in mark schemes, that some answers require facts and others require reasoning. Students who can do both, and know which the question is asking for, tend to outperform students who default to one mode.

If you are a science ECT walking into a department that has not done this work, you do not need to redesign the curriculum. The useful thing, often, is to frame your own lessons this way even if the scheme of work does not. Open a unit with a question. Make the working scientifically thread visible to students. Refer back to two or three big ideas across the year, deliberately, so students start to notice the recurrence. None of this requires departmental permission.

The trap is overdoing it in the first year and exhausting yourself. Pick one big idea and one or two big questions per term to anchor your teaching. Let the rest come more gradually. Departments that have rebuilt their KS3 curriculum around big ideas usually report it taking two or three years before it really stuck, and they had whole teams working on it. As an ECT, a steady drip is more sustainable than a redesign.

The main resources worth knowing about are Wynne Harlen's 'Principles and Big Ideas of Science Education' (free to download and the best single text on the framework), the ASE's published curriculum guidance, the Best Evidence Science Teaching (BEST) resources from the University of York which align with a big ideas approach, and the EEF's guidance on improving secondary science. None of these is prescriptive; each is a way of thinking about the same problem.

For day-to-day teaching, Cognito's GCSE Science content (Biology, Chemistry, Physics for AQA, Edexcel, OCR) is built around short topic videos, quiz questions and spaced retrieval, which fits naturally with a curriculum that wants to revisit big ideas across years. It is not a curriculum design tool; it is a delivery layer. The point being that big ideas thinking does not require ditching the resources you already use. It changes the way you sequence and frame them.