A subtest score is the result of a specific part of a standardized test. It helps measure distinct skills like reading or math, giving a clearer picture of a student's abilities.
Research from the National Home Education Research Institute (NHERI) shows that homeschooled students typically score 15 to 25 percentile points higher than public school students on standardized academic achievement tests. Most homeschool families report completing core academic subjects in 3-4 hours per day for elementary students, compared to the 6-7 hours typical of traditional schools, due to the one-on-one instruction and absence of classroom management overhead (NHERI, 2024).
What is a subtest score?
A subtest score comes from a specific section of a standardized test. Big tests like the Iowa Assessments or Stanford Achievement Test have these mini-tests, each focusing on a skill area. For instance, a reading test might have subtests for vocabulary and comprehension, each giving its own score. These scores can be combined for a broader view of academic performance. Knowing these scores helps parents see their child's exact strengths and weaknesses better than just looking at overall scores.
How to interpret subtest scores
Subtest scores come with different metrics. Percentile rank shows how your child compares to others. If your child is in the 72nd percentile for math, they scored better than 72% of their classmates. Stanines use a scale of 1-9; scores of 4-6 are average, 7-9 are above average, and 1-3 are below average. States often use the 4th stanine as a minimum. Grade equivalents, like 5.7, can be confusing. If a 4th grader scores 7.2, it means they handle 4th-grade tasks as well as a typical 7th grader would, not that they read at a 7th-grade level.
Why subtest scores matter for homeschoolers
Composite scores can hide important details. A child might be in the 95th percentile for math problem-solving but only at the 45th percentile for computation. This creates an average score that misses both strengths and weaknesses. Checking subtest scores helps you see where your child shines and where they need help. This way, you can adjust your curriculum effectively. Instead of overhauling your math program, you might just add some practice on math facts while advancing in concepts. Plus, tracking subtest scores year after year helps you see growth patterns better than just composite scores.
State requirements and subtest scores
State rules differ a lot. For example, North Carolina wants specific subtests in reading, grammar, spelling, and math. Virginia requires a composite score at or above the 4th stanine but allows lower individual scores as long as the overall score meets the mark. States like Oregon set minimums around the 15th percentile for composite scores. Eleven states require assessments but no minimum scores, while another eleven have no testing requirements at all. Always check your state’s rules to know which scores you need to pay attention to for compliance.
The bottom line
Subtest scores give a detailed look at academic performance, unlike composite scores. While your state may only require composite scores, looking at individual subtests provides useful information for planning your curriculum. If a vocabulary subtest is strong but comprehension is weak, that points to specific teaching needs that a general reading score would miss. Use subtest results to spot patterns: maybe your child struggles with processing speed or has gaps in certain skills. The same test given each year lets you track if your instruction is helping.
