Kindergarten readiness
2 IQ points behind on day 1The kindergarten readiness battery tests letter recognition, number sense, and working memory, which makes it a rough IQ proxy. Lanphear’s 1,333-child pooled analysis found 1 IQ point lost per 2.4 µg/dL of mean childhood blood lead. A toddler who averaged 5 µg/dL enters kindergarten about 2 points behind a zero-lead peer. You will not see it in the room, but it shows up on every test after.