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The outlier score is not necessarily of clinical significance in and of itself. Without additional information, it's difficulty to offer possible interpretations of the lower Si score. The child's age, past testing history, reading/writing interests and experience, expressive/receptive language skills, etc. may all contribute to this interpretation. If you feel comfortable, perhaps you could share a bit more about your child's learning profile.

...pronounced like the long vowel and first letter of the alphabet...