6 Plan B: Out of age range assessments and age equivalent scores

Developmental assessments in older children

Some children will not be able to complete standardized, age-appropriate measures, even when using tests with “low floors,”  and with appropriate accommodations. This is often the case for children who’s developmental level is below approximately age 3. For these children, one way of conducting a structured assessment of developmental level is to use one of the infant (developmental) assessment measures such as the Bayley-4. These measures are designed to directly measure developmental level through a series of interactive activities. Doing a developmental assessment allows for documentation of functioning through developmentally appropriate assessment materials.

However, developmental assessments are designed for children with typical motor and sensory functioning. For children with multiple, severe disabilities, you may only be able to complete certain parts of a developmental assessment (e.g., if a child has significant motor or sensory dysfunction). For example, the Bayley-4 Cognitive asks children to place blocks in a cup, which would be impossible for some children with severe motor disabilities. Also, if there is a query of Autism, self-directed behaviour may interfere with the child’s ability to follow directions and thus results could under-estimate capabilities.

Using a developmental measure, you will get valuable direct observations of the child’s developmental capabilities. For example, do they have object permanence? Do they understand simple cause and effect reasoning? What level of play skills do they demonstrate? If you are able to complete a full measure, you can also calculate age equivalent scores. An age equivalent (AE) score indicates the age at which a given raw score is equal to the median (or mean) raw score for a particular age level.

Limitations of age equivalent scores

• AE scores are an ordinal, not a ratio or an interval scale of measurement. They cannot be added, subtracted, or averaged. Being ordinal, a 3 month difference at age 4 can be very different than a 3 month difference at age 14.
• AEs do not take into account the range of normal performance. A child age 8:0 with an AE of 6:10 on WISC-5 Vocabulary may appear to be impaired based on the AE, but this is equivalent to a Standard Score of 8 (Average).
• AEs are not comparable across subtests (even on the same test). For example, you may see an AE score on the WIAT Word Reading subtest which is lower than the AE score on WIAT Numerical Operations subtest, even though Word Reading has a higher standard score compared to Numerical Operations.
• A 14 year old who scores at the 12 month old level on the Bayley-4 has a very different developmental experience than a typical 12 month old infant. It is unlikely that they function like a typical 12 month old child.

So what to do? Be aware of the limitation of AE scores. Use AEs when they are useful, but interpret with caution and only in the context of a broader assessment of the child.