Telling
In the past adoption was often cloaked in mystery. Nowadays it is always felt to be in the best interest of the young person for them to know about their adoption.
Depending upon the age and understanding of the child, the topic can and should be brought up as early as possible. Naturally the child will have a number of questions regarding their birth family. Some of these questions you will be able to answer and others you may not.
It is a good idea for you to consider how you should go about telling the child about the adoption before they start asking questions themselves. There is a variety of information available to offer you advice on all these aspects of adoption.
A young person's experience
Sam's Story [PDF] - A young adopted adult talks about his experience of growing up adopted.
Resources
Raising Adopted Children by Lois Ruskai Melina - Part II Chapter 4 offers some guidance on talking about adoption with children
Telling the Truth to your Adopted or Fostered Child - Betsy Keefer & Jayne E. Schooler
Talking to children about being adopted [PDF]
New Life Work Model Practice Guide -A guide by Edith Nicholls on helping your child to make sense of their birth family history.
Talking About Adoption by Marjorie Morrison - Practical guidance on why telling your child is so important, what to tell your child and when, and the responsibilities you face if your child is of a different ethnicity, from a different country or has disabilities.