There is a remarkable difference between simultaneous and sequential bilinguals, mainly because in the first case all languages are acquired at the same time. In the second case, the first language interferes with the following languages. That's why it's important to pick the right strategy for teaching.
Also please note that your child may go under acquisition and learning at the same time!
![](https://s2.save4k.ru/pic/4TdnL95XPSk/mqdefault.jpg)