Oh, and one more thing, I notice that the previous Lexile was obtained in kindergarten. The kindergarten (K-2) version of the test is quite different from the 1-12 version, as it focuses on foundational decoding skills, predicting, rather than measuring, reading comprehension. So in addition to the issue of SEM, the two administrations don't necessarily compare apples to apples.

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