Read words that end in ck after a short vowel, and read words with double consonants (ll, ss, ff, zz) that make just one sound.
Short words with a short vowel sound often end in "ck," like "back" and "duck." The c and k team up to make one crisp k sound at the end.
Some words end with two of the SAME letter, like "bell," "miss," "huff," and "buzz." Even though you see two letters, you only say the sound once.
Mastery looks like: They read ck and double-letter endings smoothly, saying the sound once even though they see two letters.
Common stumbles: Trying to sound out both letters of a double pair separately, like l then l again.