Why Is There a Different High-Frequency Word Checklist for the Same Level at Different Grade Levels?

The sight words on the high-frequency word checklists match the words taught in the lessons. The collection of books used in Kindergarten, Grade 1, and Grade 2 are different, and we only teach words that show up in the books. That's why there's a discrepancy between grades. At the higher text levels, when new sight words are introduced at a faster rate and vary more widely, you may see an even greater difference across grades.