Put the tip of your tongue between your teeth — you should be able to see it. Blow air over it — thhh. Voice off.
Check yourself: Mirror. If you cannot see the tongue tip, it is not out far enough.
Watch for: /t/, /s/ and /f/. All three are what a child reaches for when the tongue will not come out.
◆ marks a word that does NOT follow today's pattern — Blumenfeld boxes these on the page. Teach it by heart; do not let the class sound it out and lose faith in the rule.
Say the word, have them repeat it, count the sounds on fingers, THEN write. The count is what stops a child writing the first letter and guessing the rest.