What Dyslexia Is (and Isn’t)
Dyslexia is one of the most common learning disabilities, and nearly every teacher teaches students who have it, whether or not they have been identified. This module gives you a clear, current definition, explains what causes dyslexia and what doesn’t, clears up common myths, and shows why strengths matter.
The module has three parts. Each part has a short reading followed by practice activities built around real classroom moments. Work through the sections in order; your progress is saved as you go. Plan on about 35 minutes, including the video.
- Define dyslexia using the International Dyslexia Association’s 2025 definition
- Explain that the core difficulty is reading and spelling words
- Describe what causes dyslexia and what doesn’t
- Recognize and correct common myths
- Use the Simple View of Reading to explain why listening helps
Watch first: What Dyslexia Is (and Isn’t) (7 min)
Watch the overview, then work through the readings and activities below.
The 2025 Definition
In 2025, the International Dyslexia Association (IDA) released its first major revision of the definition of dyslexia since 2002. It describes dyslexia as a specific learning disability marked by difficulty with word reading and/or spelling, involving accuracy, speed or both.
Two parts of the definition matter most for teachers. First, the difficulties persist even with instruction that works for a student’s peers. Second, dyslexia falls along a continuum from mild to severe; there is no single cutoff where it begins.
Read the IDA’s 2025 definition page. Notice what the definition says about underlying skills, early oral language and secondary consequences.
Open the IDA 2025 definition →- The core difficulty: word reading and spelling
- Accuracy, speed or both
- Persisting despite instruction that works for peers
- A continuum of severity
- Underlying phonological and morphological skills
What Teachers Should Know About the Definition
Keep these ideas in mind when a student’s reading worries you.
The core is word reading and spelling.
Students may read words inaccurately, or accurately but very slowly. Spelling is almost always affected.
Speed counts, not just accuracy.
Some students read words correctly but so slowly that comprehension and stamina suffer.
It persists despite good teaching.
The key signal is slow progress with instruction that works for classmates.
It’s a continuum.
Dyslexia ranges from mild to severe, and needs vary along that range.
Leah, a fifth grader, scores in the average range on your reading comprehension quiz when she has as much time as she needs. During timed classroom reading she finishes about half the passage, and her oral reading is accurate but very slow and effortful.
Her spelling in journal entries is full of errors, even on common words. A colleague says, “She gets the words right, so it can’t be dyslexia.”
You decide to bring examples to your team.
Which evidence is most useful?
Which phrase from the 2025 definition best helps teachers tell dyslexia apart from a lack of instruction?
Reveal the Best Answer
For each statement, choose Accurate or Inaccurate, then check your answers.
1. Dyslexia can involve slow word reading even when accuracy is good.
2. Dyslexia is defined mainly as a problem with understanding ideas.
3. Dyslexia falls along a continuum from mild to severe.
4. Spelling is rarely affected in dyslexia.
What Causes Dyslexia, and What Doesn’t
The causes of dyslexia are complex. The 2025 definition describes combinations of genetic, neurobiological and environmental influences that interact over development. Dyslexia often runs in families.
Just as important is what does not cause dyslexia: laziness, poor parenting, vision problems or low intelligence. Dyslexia is language-based, and it occurs at every level of ability.
Read the IDA guide Dyslexia in the Classroom: What Every Teacher Needs to Know. Focus on the sections describing dyslexia and its common signs and myths.
Open the IDA teacher guide →- Dyslexia is language-based, not visual
- It occurs across all levels of ability
- Common myths teachers hear
- How dyslexia can affect students emotionally
Myths and Facts
You will hear these myths from colleagues, families and students.
Myth: Dyslexia means seeing letters backwards.
Letter reversals are common in all young writers. Dyslexia is a difficulty with language, especially the sounds and parts of words.
Myth: Students with dyslexia aren’t very bright.
Dyslexia occurs at every level of ability, including in gifted students.
Myth: Kids outgrow it.
Dyslexia is lifelong, but explicit instruction can make a big difference, especially early.
Myth: It’s caused by poor parenting or not reading at home.
Genetic and neurobiological influences play a major role; families often share reading difficulties.
A parent tells you her first grader, Theo, “sees letters backwards” because he sometimes writes b for d. She has scheduled a vision exam and wants to wait for the results before anyone at school looks at his reading.
Your notes show Theo is slow to learn letter sounds, struggles to blend sounds into words, and has trouble with rhyming games.
Theo’s mother asks what she can do at home.
What is the most helpful suggestion?
Which of these is NOT a cause of dyslexia?
Reveal the Best Answer
For each statement, choose Accurate or Inaccurate, then check your answers.
1. Dyslexia often runs in families.
2. Letter reversals are the main sign of dyslexia.
3. Students with dyslexia can be gifted.
4. With enough time, most students outgrow dyslexia.
The Simple View of Reading
The Simple View of Reading says reading comprehension depends on two things: word recognition (getting the words off the page) and language comprehension (understanding the words once you have them). A student needs both.
Dyslexia mainly affects word recognition. That is why many students with dyslexia understand far more when text is read aloud, and why listening to text can keep them learning grade-level content while their reading skills grow. Over time, reading less can also slow vocabulary and knowledge growth, which is one of the secondary consequences in the 2025 definition.
Read the Reading Rockets article on effective reading instruction for students with dyslexia. Notice how it connects word recognition to comprehension.
Open the Reading Rockets article →- Word recognition versus language comprehension
- Why listening comprehension is often a strength
- How reduced reading affects vocabulary
- Why both instruction and access matter
Strengths and Co-occurring Needs
Look at the whole student.
Strong listening comprehension
Many students with dyslexia understand and discuss complex ideas well when they hear them.
Reasoning and creativity
Many are strong problem-solvers, discussers and big-picture thinkers.
Dysgraphia and ADHD often co-occur
Handwriting and written expression difficulties and attention difficulties are common alongside dyslexia.
Reading anxiety
Years of struggling in front of peers can lead to avoidance and worry.
Ana, a fourth grader, leads some of the best class discussions and remembers every detail of a read-aloud. Her oral reading is slow and effortful, and her spelling often sounds right but is missing letters.
Lately she asks for the bathroom pass whenever independent reading starts. A colleague says, “She’s just avoiding work.”
While the team looks closer, how can you keep Ana learning grade-level content?
Choose the best support.
A student understands a grade-level science text well when it is read aloud but not when reading it alone. Which part of reading is most likely the barrier?
Reveal the Best Answer
For each statement, choose Accurate or Inaccurate, then check your answers.
1. Reading comprehension depends on both word recognition and language comprehension.
2. Listening to text can help students with dyslexia keep learning content.
3. If a student has ADHD, dyslexia can be ruled out.
4. Avoiding reading is always a sign of poor motivation.
What to carry into Module 2
- Dyslexia is a specific learning disability in word reading and spelling: accuracy, speed or both.
- It persists despite instruction that works for peers and falls along a continuum.
- It isn’t caused by low effort, vision problems or low intelligence.
- Notice strengths, especially listening comprehension, and look for patterns.
References
- International Dyslexia Association. (2025). 2025 definition of dyslexia. https://dyslexiaida.org/2025-dyslexia-definition-project/
- International Dyslexia Association. (n.d.). Dyslexia in the classroom: What every teacher needs to know. https://dyslexiaida.org/?p=1311
- Gough, P. B., & Tunmer, W. E. (1986). Decoding, reading, and reading disability. Remedial and Special Education, 7(1), 6–10. https://doi.org/10.1177/074193258600700104
- Reading Rockets. (n.d.). Effective reading instruction for students with dyslexia. https://www.readingrockets.org/topics/curriculum-and-instruction/articles/effective-reading-instruction-students-dyslexia