I have spent more than a decade writing about vocabulary and working with a range of teachers across primary, secondary and colleges. Over that time, I've come to think differently about one of the most important, but tricky aspects of vocabulary instruction: deciding which words to explicitly teach.

Many teachers are familiar with the 'SEEC model' (select, explain, explore, consolidate). It works well for explicit vocabulary teaching. Teachers select a small number of words, explain them with student-friendly examples, explore them further through morphology, synonyms, and more, and then consolidate them through repeated exploration, recall and use.

However, in practice teachers often struggle with the first step: select.

The challenge of vocabulary selection

The challenge is obvious. Teachers simply do not have time to teach every unfamiliar word students encounter or find tricky.

We can be caught between a vocabulary teaching rock and a hard place. Too much pre-teaching can slow the rhythm of teaching. If we pause to explain every tricky word in detail, we risk losing the flow of reading and never quite finishing the lesson with the depth we intended. And yet, if students misunderstand or don't know important vocabulary in what they read, their learning can be stunted.

The excellent and now widely-known vocabulary tiers, developed by Isabel Beck and Margaret McKeown, have long helped teachers think about vocabulary selection. Their model appears in literacy guidance from the Education Endowment Foundation and remains an important framework to think about selecting words to teach.

Yet, I am commonly finding the teachers can struggling to meaningfully apply the tiered model consistently to their teaching without sustained support.

In some cases, Tier 1 vocabulary is largely ignored, while teachers enthusiastically search for lists of Tier 2 words to teach explicitly. These words can end up taught somewhat in isolation: repeated in quizzes or placed into sentences that are only loosely connected (or not at all) to the texts students are reading. Identifying a smaller number of Tier 2 words to teach can have value, but trying to cover every word in the curriculum with explicit instruction is not the aim.

Academic word lists (like the Avril Coxhead 'Academic word list') can offer a useful starting point for thinking about the Tier 2 words students need to know, but I rarely see a place for teaching them exclusively as a bolt on to the taught curriculum, without any meaningful integration into specific topics or reading texts. We need careful consideration about the few Tier 2 words that get curriculum time.

Teachers may feel compelled to teach every Tier 3 word they encounter to alleviate issues for students who struggle. The result can be an unmanageable number of words competing for attention, with too little unpicking of what few words to teach and why to do so. Even ins a subject like science, it is so dominated by Tier 3 vocabulary, that explicit instruction requires careful selection.

The key issue is that, for the majority of the time, vocabulary selection should be rooted in the meaning of the text being read – whether that is a poem, a worksheet, a science textbook chapter, or a case study in geography - rather than in a separate word list of important subject terminology (though there is a place for recording such vocabulary).

A considerable amount of academic vocabulary growth happens through reading rich curriculum texts. The words in what we read in class are uniquely rare and special - so vocabulary and reading instruction are a natural pair. We still need to identify words to teach before reading and after reading, but it is usually better done thinking also about what is being read.

'Keystone' and 'bridging' vocabulary

When selecting vocabulary from meaningful reading and instruction, I have increasingly found it helpful to distinguish between two types of academic vocabulary: 'keystone vocabulary' and 'bridging vocabulary'.

  • Keystone vocabulary refers to words that hold together the central meaning of a text. If students do not understand these words, their comprehension of the passage – and often the wider topic – will be compromised. These words therefore deserve explicit and extended teaching.
  • Bridging vocabulary refers to words that can be briefly explained in order to support fluent reading. These words matter, and they may well be useful in the long term, but they are not essential to understanding the core concept/s of the text.

A simple rule of thumb helps clarify the difference:

  • Without keystone vocabulary, comprehension falls down.
  • Without bridging vocabulary, reading becomes less fluent but understanding remains possible (though likely impaired).

Using this distinction can make vocabulary selection far more manageable and replicable in the classroom:

Step 1: Scan the text
Read the text quickly to grasp its overall meaning and identify potential points of complexity.
Step 2: Identify keystone vocabulary
Re-read the text and select 3 to 5 words that carry the central meaning of the text.
Step 3: Identify bridging vocabulary
Select 3 to 9 additional words, depending on the difficulty and length of the text, where students may struggle (that can be addressed very quickly without interrupting the flow of reading)

For every textbook chapter, historian source, or geography case study, the above steps should prove both manageable and valuable.

A key test is whether you can quickly explain the bridging vocabulary item in 10 seconds or less. These words are to be very quickly addressed, with a focus on sustaining attention on a fluent reading of the text. Conversely, keystone vocabulary will be allotted more teaching time, either before or after reading.

Listening to pupils read a text aloud can also be revealing. The words where students hesitate or stumble often highlight exactly which vocabulary disrupts fluent reading.

A worked example from geography

Consider a short geography explanation of the concept of slab pull:

'Slab pull is a process that helps drive plate tectonics. It occurs at a subduction zone, where a dense oceanic plate moves beneath another plate and sinks into the mantle. As the plate gets older, it becomes colder and denser than the surrounding rock. Because of this density difference, gravity pulls the sinking edge of the plate downward. This downward force drags the rest of the plate behind it, helping the tectonic plate move across Earth’s surface.
Scientists often describe slab pull as one of the most significant forces controlling plate movement. The process involves the gradual descent of the plate into the mantle and the transfer of energy through the lithosphere. This movement can influence volcanic activity and earthquakes near subduction zones. Over long periods of time, the continuous sinking of plates can contribute to the recycling of Earth’s crust and the formation of mountain belts and deep ocean trenches.'

A geography teacher might identify the following words for extended instruction.

Potential keystone vocabulary:

  • slab pull
  • plate tectonics
  • subduction zone
  • mantle

These terms carry the central meaning of this particular text.

Potential bridging vocabulary:

  • significant
  • gradual
  • transfer
  • continuous
  • contribute
  • formation
  • lithosphere
  • mountain belts

These words help support understanding but are not essential for grasping the core concept. 'Tier 3' words like lithosphere may be of importance, but they are not addressed specifically in this text for instruction (though they may have featured as keystone vocabulary in other geography texts).

In many cases, this distinction loosely aligns with the tiered model. Tier 3 subject vocabulary often functions as keystone vocabulary, whereas Tier 2 vocabulary frequently acts as bridging vocabulary, supporting fluent reading.

The keystone and bridging distinction can be applied across subjects. Subject experts already make many of these decisions instinctively when guiding students through tricky texts. The approach simply offers a clear language for describing those manageable lesson planning judgements.

For example, when teaching William Blake’s poem London, a teacher might quickly identify the following keystone vocabulary: such as "charter’d", "ban" and "mind-forg’d manacles". Alongside these, bridging vocabulary might include: "appals", "marks", "hapless", "harlot", "blights" and "hearse".

In English literature lessons, unpacking meanings in this way is already common practice (though hugely varied by teachers, so perhaps less easily picked up by students). Teachers do regularly pause to explain how vocabulary contributes to meaning, amongst other literary features, but the distinction for identifying words to teach still stands.

Across other subjects, however, the connection between reading a text, selecting vocabulary and teaching a topic is often less deliberate. A teacher may highlight important ideas and vocabulary, but the process is not always explicitly tied to the act of reading.

Teaching vocabulary: a balancing act

Teachers will always feel the temptation to teach every unfamiliar word or aim for a check for understanding. Research in second-language learning often suggests readers benefit from knowing around 95 per cent of the words in a text. In practice, classroom reading of complex academic texts in your first language often requires working below that threshold (this is no exact percentage for this).

The task, therefore, is not to teach every word but to teach the right words, at the right time, for the right amount of lesson time.

By focusing explicit instruction on keystone vocabulary, while briefly explaining bridging vocabulary during reading, teachers can preserve the flow of a lesson, whilst still building a rich academic vocabulary for every student (especially those who struggle with words in school and beyond).

Done well, this approach does more than add new words to students’ personal word-hoard. It helps give them the language that unlocks meaning and makes complex reading accessible.

  • My blog on 'Three Pillars of Vocabulary Teaching' explores where explicit vocabulary instruction fits, alongside building vocabulary implicitly and encouraging student's 'word consciousness'. READ IT HERE.
  • Strong evidence supports a focus on teaching word parts - morphology - when it comes to explicit vocabulary instruction, which my blog on 'Teaching Vocabulary and Mighty Morphemes' explains. READ IT HERE.
  • Carl Hendrick wrote a compelling blog on reading and the importance of vocabulary instruction recently, entitled 'Reading comprehension is not a skill'. READ IT HERE.

On Friday 26th June, I'm doing an in-person all-day Teachology masterclass on 'Reading and Vocabulary Essentials'. I explain why they are essential - drawing upon insights from my new book - as well as pose practical reading and vocabulary routines for every teacher. I walk through selecting words to teach and how to teach them, alongside how to build brilliant book talk, and develop confident fluent readers. FIND OUT MORE HERE.