Experts stress separating the languages to make language acquisition easier for kids. When kids are learning two languages at the same time parents need to work out language strategies that emphasize boundaries between the languages. Both parents speak one language in the home and a second language is used at school. One language is used in the home and at school and the second language is used in the community. Both parents speak both languages to the child but separate the languages according to speaking situations or alternate days.
Consistency is key in early language learning.
If you mix languages in the same conversation, young kids experience difficulty separating vocabulary and grammar into the appropriate language. Parents also need to consider how to strike a balance between the languages. If a child attends school in one language all day and has only a short time to hear the other language at home, it's likely the school language will develop more easily than the home language. Parents have to plan for additional time spent using the home language in a variety of situations and with a variety of speakers. Rich language experiences in both languages are essential for good bilingual development.