ADHD T Score Explained: What the Numbers on Your Child's Report Mean

What a T-Score Actually Represents

A T-score is a standardized number that tells you where your child's reported behavior falls compared to a normative sample of age-matched peers. Every T-score has a fixed structure: the average is set at 50, and each 10 points equals one standard deviation from that average.

When an evaluator hands you a report showing a T-score of 68 on an Inattention scale, that number means: the rater described inattentive behaviors that are 1.8 standard deviations above what the average child's raters report. It does not mean your child scored 68 out of 100. It does not mean your child got 68 percent of the questions "wrong." It is a relative position within the normative distribution.

The T-Score to Percentile Conversion

T-scores and percentiles measure the same thing from different angles. A percentile tells you what proportion of the normative sample scored at or below that level:

The jump between percentiles accelerates at the tails. Moving from T-score 50 to 60 spans the 50th to 84th percentile—a 34-point shift. Moving from 60 to 70 spans the 84th to 98th percentile—a 14-point shift. Both are 10 T-score points, or one standard deviation; the percentile intervals differ.

Why Different Tests Label the Same Score Differently

One of the most confusing aspects of evaluation reports is that different rating scales use different labels for the same T-score ranges.

A T-score of 65 is labeled "Elevated" on the Conners 4, "At-Risk" on the BASC-3, and "Potentially Clinically Elevated" on the BRIEF-2. All three labels describe the same statistical reality: the child's behavior on that scale exceeds approximately 93 percent of the normative peer group. The labels differ because each publisher designed their own classification system.

When reviewing a report that uses multiple instruments, look at the numbers first and the labels second. A Conners 4 "Slightly Elevated" at T-score 62 and a BASC-3 "At-Risk" at T-score 62 are the same finding described with different words.

What "Clinically Significant" Means

On most ADHD-related rating scales, a T-score of 70 or above is classified at the highest clinical level. The BASC-3 calls it "Clinically Significant." The Conners 4 calls it "Very Elevated." The BRIEF-2 calls it "Clinically Elevated."

Whatever the label, a T-score at or above 70 means the child's behavior in that domain is more extreme than 98 percent of age-matched peers in the normative sample. In educational terms, this is strong quantitative evidence that the child has a substantial limitation in a major life activity—the standard Section 504 uses to determine eligibility for accommodations.

A T-score of 70 is not the only number that matters, though. A score of 65 places the child above 93 percent of peers and may be relevant evidence in a 504 or IEP evaluation, even though the label may not say "clinically significant." No single score establishes eligibility. Schools sometimes argue that scores below 70 are "not bad enough" to warrant support. That argument misrepresents what Section 504 requires—a substantial limitation, not a specific T-score cutoff.

When Direction Flips

On scales that measure clinical problems (Inattention, Hyperactivity, Anxiety, Depression), higher T-scores mean more problems. But on adaptive and positive-skill scales—such as the BASC-3 Adaptability, Social Skills, Leadership, and Functional Communication scales—the direction reverses. A T-score of 35 on Adaptability is below average, meaning the child adapts to change worse than most peers. A T-score of 28 on Functional Communication is clinically significant in the low direction.

If a report says a child scored 35 on Social Skills and 72 on Attention Problems, both findings point in the same clinical direction: the child has more attentional difficulty than peers and fewer social compensatory skills.

What T-Scores Cannot Tell You

T-scores describe severity relative to peers. They cannot tell you whether the behavior stems from ADHD, anxiety, depression, a learning disability, or something else entirely. They do not measure intelligence, academic achievement, or potential. A child with a T-score of 75 on Inattention and a T-score of 50 on Anxiety may have straightforward ADHD. A child with a T-score of 72 on Inattention and a T-score of 70 on Anxiety may have anxiety-driven attention problems that look like ADHD on paper. The differential diagnosis comes from clinical interpretation, not from the numbers alone.

The ADHD Rating Scale Decoder translates T-score profiles from the Conners 4, BASC-3, BRIEF-2, and other instruments into plain-language explanations, with guidance on what patterns suggest primary ADHD versus co-occurring or alternative explanations.