The effect of instruction on second language acquisition is limited
The findings regarding the efficacy of instruction on Second language acquisition is mixed. Counterintuivitely, instruction is not always helpful.
Instruction sometimes has no effect on acquisition.
It cannot allow learners to skip steps in developmental sequences (see Learners’ output proceeds along predictable paths).
Instruction can sometimes slow down acquisition.
Instruction can sometimes speed acquisition and allow learners to reach higher levels.
The circumstances under which instruction is effective are an active and controversial area of research.