While often misunderstood in communities where the majority of children grow up with just one language, bilingualism is actually an advantage for children. According to the Center for Applied Linguistics, children who have a second language are more creative and capable of solving more complex problems than monolingual children do. In addition, they score higher on verbal and non-verbal intelligence tests and often score higher on standardized tests.

Vocabulary development
Language acquisition in bilingual learners may be somewhat different than in monolingual children, but eventually they end up reaching all the same milestones.

Bilingual children when very young may have less vocabulary in each language than children who speak only one language. That is most likely due to a limited memory capacity at a young age. If the vocabulary in both languages is totaled it will typically equal the vocabulary of a monolingual child. It's also important to note that by the time a child starts kindergarten or first grade, in most cases, the differences will be gone.

Social Communication
The development of social communication may also differ in bilingual children in the early childhood years. Often, a bilingual child has more exposure to interpersonal communication in one language and less in another.

Children in ESL classes at the preschool level will have additional opportunities to learn social language with other ESL learners as well, as native English speakers if the preschool class has both types of students. This will help the ESL students learn social contexts and meanings faster, since when given adequate exposure, the bilingual child becomes capable in most cases.

Proficiency
In general, children will develop as much proficiency in a language as he or she is given time in that language. If children only hear a second language when with grandparents, that language will be less developed than the language spoken around them most the time.

If children's parents do not speak the majority language, school personnel should encourage them to speak their native language at home to build the children's connection to their own unique culture and develop a rich and varied language background.

Mixing Languages
Sometimes people express concern that a child mixes the two languages together, often in one sentence. This is actually quite natural and not an issue for concern. According to the Center for Applied Linguistics, research has shown the most proficient bilingual speakers mix language the most and in complex ways without violating the rules of either language.

It's a normal process for bilingual learners and ESL teachers should not correct or discourage children from the practice, as it is not a sign of not understanding the differences between the languages at all.

Types
A preschool ESL class typically has students with many different primary languages and includes English as a second language. Preschool ESL classes have many different approaches and some schools use a variety. One common method is transitional bilingual education or TBE. Often, this means children first receive intensive English classes, and then receive academic classes taught in the primary language.

Dual-language preschool ESL classes have native English speakers as well as English language learners. Instruction is in both languages with the goal of all students becoming bilingual.