Though many families do not set native-like proficiency as the goal and don’t need to, the statements below once again emphasize the importance of listening and speaking proficiency by 5 and then by 8.
Wikipedia: second language learning
“…..children by around the age of 5 have more or less mastered their first language, with the exception of vocabulary and a few grammatical structures.”
“In acquiring an L2, Hyltenstam (1992) found that around the age of six or seven seemed to be a cut-off point for bilinguals to achieve native-like proficiency. After that age, L2 learners could get near-native-like-ness but their language would, while consisting of few actual errors, have enough errors to set them apart from the L1 group. The inability of some subjects to achieve native-like proficiency must be seen in relation to the age of onset (AO). “The age of 6 or 8 does seem to be an important period in distinguishing between near-native and native-like ultimate attainment. More specifically, it may be suggested that AO interacts with frequency and intensity of language use” (Hyltenstam, 1992, p. 364).”