Haven't got much to add to the reply above, but wanted to add another "thumbs up" so to speak.
I speak language 1 (one of my "birthlanguages", am bilingual) with our DCs, have done so from birth. DH speaks language 2, has done so from birth. DH and I speak language 2 to each other, so it is our "home language". He's native, I can pass for one...
DS was an early speaker, and had a pretty impressive vocabulary in language 1, very early on... also early with sentences and "proper structure". Language 2, despite it being our home language, took a while, but then DH wasn't exactly taking an active interest and chatting/reading to DS as he found it awkward. DS was 22 months when he started daycare, straight into language 3, which he'd had virtually no exposure to before starting daycare. He found the first month or so hard, but definitely had a passive vocabulary in just a few weeks. Three months in, his active vocabulary was on the same level as the rest of the group.
Language 2 took the longest to "crack", in terms of active vocabulary, but improved very quickly once DH took an active interest. DS is nearly 4 now, and is at native level in all three languages... in fact, I'd go as far as saying he IS native in all three: how could he not be? He lives and speaks all three every day! :)
DD was a bit older than DS when she first spoke, but still relatively early. She did seem to find it harder to differentiate between languages, or something... not sure how to describe it, but I spent quite a while thinking she was "babbling" or talking jibberish until I suddenly realised that she was actually using words in all three languages, but I was only listening out for language 1 and not really picking up what she was trying to say... I'm not really explaining this very well at all, sorry... I guess, a bit like thinking "Hola" is a cute babyish way of saying "hello", and then realising that it's NOT a cute babyish way of saying "hello", it is actually a word in its own right? (Best example I can come up with, sorry... none of our three languages are really related...)
Anyway... DD went to daycare at 10 months, straight into language 3. I was very, very, very worried about this, due to the reasons the poster above explained so much better than I ever would...
In hindsight, it hasn't harmed her. She picked up language 3 very quickly, and in a couple of months she had a passive vocabulary that was "functional" (she understood what she was told/asked)... hard to say how difficult she found it as starting daycare itself was such a big transition... She's now 18 months. Language 1 is definitely strongest. Language 2 not too far behind, and she has just now started speaking language 3.
I agree with Smoutebollen: it's an investment of time, patience and commitment from the parents. I'd also say it requires the same - and understanding, willing people - at daycare. (Not a given...)
The staff at DCs daycare are brilliant, and they've enjoyed watching the process with DD. But then they are generally lovely and accomodating, just now I had a call as DH is picking the DC up, but something got lost in translation so the staff called me to explain. They really don't mind going the extra mile.
I have at times worried about "overloading" DD, even though we had such a positive experience with DS... he was so much older! But then I've had similar worries about DD being in daycare at such a young age too...
Bottom line - this is the only reality our DC know. Three languages to them is normal. Yes, they've probably been thrown in at the deep end according to some, but they're very capable swimmers now. :)
(I hope this continues to be a positive experience for all of us as they grow. The plan is that they will also go to school in language 3, as that is nearest... Smoutebollen has a good point about homework, but luckily lan3 is the other of my "birthlanguages" so hopefully fine...)
a few interesting observations along the way:
- DC mainly speak language 1 to each other, but I've noticed that if they're playing on their own, they use whatever language the last parent to interact with them did IYSWIM?
- DH says if they are with him, and everyone is speaking lan2, DS will comfort DD in lan1 if she gets upset. (awww... :) )
- DS now "translates" automatically to us parents, which makes for double the chatter. This can get a bit tedious around the dinnertable... If DH tells DS something in lan2, DS then translates this to me and lan1, even though lan2 is the one we all have in common... and so on... so, it's time consuming and noisy. :)
- I find it fascinating how both DC keep checking the languages. If they learn a new word in one language, they ask what it is in the others, and keep checking. It's like the learning process isn't complete until they've got it in all three languages. (I'm sure this will change though, and eventually they'll probably have different strenghts and weaknesses and context specific vocabularies... )
- DS doesn't like me reading stories or singing in the "wrong" language.
Sorry this is so long and rambling, it was supposed to be a short post as am rushing and at work... but it's fascinating!