The teaching of grammar plays a major role in any language classroom, and traditionally follows the (hidden) curriculum of the textbook used in the classroom. In the past, competing approaches to grammar teaching have been put forward, but the majority have not been inspired by a theory of language nor by findings from second language acquisition (SLA) research. As implicit learning of (interlanguage) grammar is crucial in any instructed setting, however, findings from SLA research contribute to making foreign and second language teaching more efficient. One core finding is that practice does not necessarily make perfect, as it is a vital but not a sufficient prerequisite for language acquisition.