My child has recently been administered the WISC-V. The Vocabulary, Block Design, Visual Puzzles, Matrix Reasoning, Figure Weights, Digit Span and Coding scores are all 18-19, but the Similarities subtest score is a 12. I am not concerned but am also unsure how to interpret this outlier. I would appreciate any helpful insights.

Welcome!

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.