Life in the foster care system is often difficult. Not all children end up in a home with loving foster parents who care about them. Instead, some come from impoverished situations and are placed in homes that are better from an economic standpoint, but these placements still aren't ideal for the children.
When parents adopt a child who isn't an infant, there are some specific things that might impact the child. It is important that adoptive parents take the time to find out what they can do to help the children adjust to the fact that they now have a permanent family.
Simply trying to get over the fears that come with an impoverished upbringing can be hard. Some of these children will try to hoard food. This isn't because they think you are going to starve them. More than likely, they know you won't but they are just nervous because they know what it is like to be severely hungry without any knowledge of where their food will come from.
Another issue that you might find is that they have a "me against the world" mentality. It is hard for them to understand that someone truly loves them. For this reason, you might need to rethink the idea of time-outs away from people and use a space that is near everyone so they don't feel alone.
You will likely need to encourage them to talk. Children who are adopted beyond infancy might try to keep their feelings and needs hidden out of fear that you will want to give them up if they aren't perfect. This is a hard position for them to be in, but as their new parent, you can help them to learn confidence and acceptance.
Source: Parents, "Helping Adopted Kids Adjust," Shannon Greer, accessed May 25, 2018