In k-2 literacy, systematic phonics instruction is widely recognized as the most effective approach for teaching children how to read. So why are so many students still behind? Parents may see that their child is indeed working on phonics sounds in school. Teachers may use curricula that emphasis teaching phonics sounds explicitly. And yet, instruction is still not working. What’s missing?
To reach every child, teachers need curricula that teaches the relationship between letters and sounds in a careful, sequenced way. In addition, they also need curricula that uses interleaving.
What is interleaving? It’s probably one of the most important yet overlooked aspects of effective phonics instruction. Interleaving is the intentional mixing of old and new content. For example, if a child has recently learned short vowel consonant blends, silent e and is learning ee… a practice list would include ALL of these sound patterns, not just one.
Interleaving stands in contrast to blocking, where students focus solely on one phonics sound. In blocking, if a child has learned “ee,” the practice list would look like this: bee, see, seem, peek, teem, need, feed. As you can see, blocking promotes guessing and very little cognitive work, as the child quickly figures out the “ee” sound is repeated.
Interleaving is much more effective. An interleaved list would look very different. If a child has learned consonant blends, silent e, and is learning ee, an interleaved list would look like this: seem, bike, clamp, seek, deem, brim, hope, flag, seem, bee… etc. With a list like this, a child cannot guess. A student must do the cognitive work to decode each word. In addition, the child has learned all the sounds in the list systematically. Thus, he has the skillset to decode each word.
At first glance, an interleaved list might seem more confusing or harder for students—but that’s exactly why it’s so effective.
Reading Elephant printable phonics books use interleaving.
When learners are asked to discriminate between phonics sounds, they must pay closer attention, think more deeply, and apply what they’ve learned. All this work amounts to more retention. The learner can shift information and skills into their long-term memory. Interleaving creates harder practice sessions, but it’s what cognitive scientists refer to as a “desirable difficulty.” A desirable difficulty is a positive difficulty that creates more robust, long-term learning. In phonics, this means students are more likely to remember letter-sound relationships in interleaved lessons.
For example, imagine a child learning the difference between ship and shop. If they only practice short /i/ words for a while, they may not notice how the vowel sound changes the meaning of the word. But when ship appears right next to shop, the contrast forces them to listen carefully and attend to how the vowel affects pronunciation and spelling. This comparison strengthens both decoding and encoding skills.
Interleaving prevents students from guessing at the words.
Interleaving is also important for reading flexibility. When we read, text doesn’t appear in neat, repetitive chunks. It’s important to teach phonics systematically. However, as soon as a child knows more than one phonics sound, educators should mix the phonics sounds in the lessons so the child can’t guess at the words.
Books and sentences include a mix of phonics sounds and word types. By interleaving instruction, teachers better prepare students for authentic reading experiences. Children who regularly switch between sound patterns and spelling rules during practice are more adaptable when they encounter unfamiliar words in context.
Importantly, interleaving should still be used within a systematic structure. It doesn’t replace the need for explicit, sequential instruction; instead, it enhances it. Once students have been directly taught a new phonics pattern, interleaving helps reinforce and connect that knowledge to what they already know.
This means if a child has leaned short vowels, consonant digraphs and is learning silent e, the list should look like the following : cap, bike, ship, tip, time, hope, cope, get, chat, match, cute, lit, kite… Notice how the list includes olds sounds the child has already learned and the new silent e sound.
In short, interleaving transforms phonics practice from rote repetition into rich, meaningful learning. By strategically mixing skills, teachers can help students develop stronger phonics skills, sharper discrimination, and greater reading flexibility. When combined with explicit, systematic instruction, interleaving ensures that children don’t just learn phonics—they master it for life.
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