Target/codes: independently decode a new A/B five-event plan and locate every source change; AC9AMUFD01. Prepare: public U, U A4, broad A/B cards; close the key.
- Welcome · 3 min. Offer a new paper music puzzle with no sound or speed requirement.
- Access · 4 min. Present A B B A B by word, circle/square print, raised symbols or neutral read-aloud. Do not mark any boundary.
- Independent plan · 5 min. Child tracks each neighbouring pair and finds where the source key changes.
- Child response · 7 min. Save first complete source sequence and every change boundary by card, drawing, AAC, pointing or neutral scribe.
- Self-check · 4 min. Child checks all five places and four gaps without an adult adding an answer.
- Close · 2 min. Consult the separate key later; after-check practice uses different sources.