Overload. The risk is giving a beginner more than they can act on, so they practise faults instead of one clean repetition. Task 16 is blunt about it: avoid over-explaining, keep things simple, and do not overload a beginning caster with technical terminology.

The mechanism is in the guide’s Structured Practice section. Teaching a skill holistically “is a good way to delay or even prevent learning”: the student repeats the whole cast with several faults, you point out the errors again and again, and little improves. The object of structured practice is to “eliminate faults as we build the skill” — one step, checked, then the next. Praise, Prompt, Leave makes the same point for group teaching: correct one error at a time, in plain declarative sentences.

The guard is sequence, not volume. Cover one or two topics per lesson, let each step build on the last, and leave time for independent practice, because a beginner who is watched every second cannot feel what they are doing.

Source

From the CI Study Guide (2025) (PDF) — Task 16, the teaching principles, and Appendix B (Structured Practice, Praise Prompt Leave).