The First Lesson
In your first lesson, you should make notes on which bilingual children speak which languages. Ask them how good their language skills are and how they acquired them. Many languages have certain grammar structures in common, for example the Romance languages French, Italian and Spanish. Within the same language family, not only grammar structures but even words resemble each other. A German native, for example, can understand Dutch at a basic level without even knowing a single Dutch word or a grammar rule.
When you have a list of the various languages and levels of your students, you can refer to that list when you prepare your lessons. Their familiarity can aid their development in the language they are learning.
Preparation for Further Lessons
Whenever you want to introduce a new grammar rule, a new tense or sentence structure, consult your list and look for similarities in the languages. You might want to ask teachers of the various other languages for help if you are not familiar with them. Make notes of similarities. They can be the same pattern of conjugating a verb, the same rule for sentence structure or the same use of a certain tense.
Even more important, though, make notes on the differences. Especially when two languages are close, many students tend to use the rules of their better language without noticing slight differences. Put them on their guard for false friends and point out probable sources of mistakes.
Different Languages – Different Advantages
The advantages for bilingual children depend on the relationship between “their languages" and the “new" language. If they are of the same family, bilingual children are quick to get a general understanding of unknown texts. Most grammar structures will be familiar to them. They have to pay attention to their vocabulary though.
If the languages come from different language families, your students might still recognize certain grammar structures and words. You would be amazed at how much two utterly different languages can have in common. Even Irish-Gaelic and Chinese use the same structure for agreeing and disagreeing.
The general rule is that the more languages your students speak, the easier it will be for them to learn yet another.
Using the Language Abilities in Class
Encourage bilingual children from the beginning to use their knowledge from other languages they know. Ask children who know another language from the same family for the meaning of words or let them tell the class what a new text might be about. When introducing a new grammar rule, ask them if they have similar rules in their languages. Compare the similarities and differences in class.Soon the bilingual children will start to look for familiar patterns and differences themselves.
The goal is to create more independent learners in your bilingual students. Give them the tools to learn and watch their natural curiousity push them to new heights. They will want to explore the new language (and possibly more languages after that) to find all the similarities and differences. Bilingual children have a real advantage in their language development, if they learn to utilize the knowledge they already have.