The human brain is structured to notice patterns and create order, based on what is already known and what is being experienced. According to the National Academy of Sciences, infants and young children seek to create order of language by starting with the smallest units and building up to more complex structures. The purpose of English education, then, is to guide young children in making these connections so that they acquire as much language as possible.
Adults can help children acquire English by engaging in specific activities that demonstrate the correct use of spelling, grammar and sentence structure. Some examples are: reading books aloud, both to and with children; completing spelling and grammar exercises; having conversations with young children, so that they can hear you using words and forming sentences correctly; and choosing to read actual books rather than textbooks, so that children are exposed to a wide variety of vocabulary and literature at an early age.
All children acquire language at different rates. Some are speaking before their first birthday, while others do not speak until they are two or three years old. Keep in mind that every child is unique and that they may be understanding much more than they are communicating. At the same time, some children race ahead of others in their language acquisition. It is helpful to be ready with more resources, such as longer books with more challenging vocabulary, as a child acquires more language.
Some children will face specific challenges to their acquisition of English. For example, The Linguist List suggests that children may need extra help if they have not said a recognizable word by 18 months or a full sentence by 3 years. These cases could indicate a hearing problem, and it would be advisable to take the child to a doctor for testing. Other children may encounter problems if they have gone through trauma early in life or if they are trying to learn more than one language at a time.