Learning about Foster children

Foster parents says teachers and foster parents both require more understanding of students without permanent families. They need "to become better trained in identifying children with different educational needs than the classic child. A child in foster care is rarely able to work and concentrate on class work when their lives are in turmoil," When placing foster children in a child care center, they have to make sure that these children our sociallly, physically, mentally ready to be placed in a childcare classroom. When children are taken from their parents and placed with strangers, then placed in a preschool with teachers who are also strangers to these children. My questions is how can this affect foster children? How can this affect the classroom and the other children in the classroom?