Social interactionist theory has its roots in the work of Lev Vygotsky, who focused on the role of linguistically fluent adults in the development of language in young children. As it applies to education, social interactionist theory argues for a direct, personally engaged role for primary teachers in the classroom. According to Vygotsky, direct  and involved social interaction with a verbally acute adult lays the groundwork for verbal fluency and intelligence in young children.

While the other answers all named legitimate social theorists, none of their work applied to the social interactionist theory of language development specifically.

The first thing to remember when teaching second language learners is that they are already fluent conversationalists in another language! This is the primary difference between facilitating primary and second language acquisition. Second language learners, in order to progress to the difficult goal of pragmatic competence, will be more stimulated and more apt to acquire language when they engage in natural conversations similar to those they will or would like to have in their real lives. Allowing learners to express themselves naturally and without constant strict supervision is key.

The best way to help students synthesize information about essay structures is to make sure that all aspects of language learning are incorporated into the process. By having students read, write, talk, and listen while composing their essays you will be developing all of their language skills, while also allowing the students to be comfortable, while combining social and solitary work.

This is a simple, but important, definition: semantic meaning refers to the meaning generated by a single word in isolation.

Beginning and early intermediate second language learners are very far away from being able to produce a text that does not require significant correction. To correct every grammatical point in a student's work at this level would be deeply discouraging to a student, and would simply overload them with information, making it impossible for them to actually synthesize the corrections. The best thing to do is to give specific, targeted feedback on a grammar point that the student can take in and learn from. Doing this over a long period of time, as the points are incrementally integrated the student will improve.

Semantic theory holds that meaning is the single most important factor and goal of all language. According to this theory, to acquire language is to gain the ability to express meaning. This theory identifies four kinds of meaning: semantic, lexical, grammatical, and pragmatic.

Teaching foreign language acquisition tends to take place in diverse classrooms. It is especially important in these settings to be educated and sensitive to the cultural and social factors influencing students in your classroom. Different cultures have different expectations of a classroom setting, and of the relationship between teachers and students, to treat all students in a homogenous way, and to aggressively press a uniformity of accent, is deleterious to the kind of individualized attention required to facilitate fluency in a foreign language.