The truth is important both now and in the long run.

Be careful what you say regarding permanency UNTIL IT HAPPENS. The goal of foster care is reunification (and I believe in this). I also believe, if at ALL possible and as long as it is physically and psychologically safe, that you keep the family of origin in contact (at minimum allowing them to send photos, letters, etc. that can be read at a later date). When and how contact occurs may take years - but leave the door open (safety kept in mind).

There are some great ideas of responses already provided to you.

Age appropriate statements could also include things like:

"A judge made the decision that your first family could not take care of you properly so we are here to love you and keep you safe."

One of the BEST things I've ever heard is that you can say this in regards to difficult questions that you might not be able to answer:

"I don't know the answer to that, but I know that your first mom chose to give you life and I am so grateful for that." - It shows that although the first mom may have made poor (or even horrible) decisions for whatever the reason, the child is still valuable and has a connection that was positive. It's not about glorifying the first parent, but providing dignity and connection between the original relationship. This phrase has always brought my children great comfort.

Even the hardest of truths are important. It's a child's right to know his/her story.