The purpose of this article is to develop, validate, and field test two readiness assessment instruments, "Schools Ready for Children" and "Children Ready for School." The authors first describe the development of the assessment instrument dealing with policies and practices of "ready" schools. The items on this instrument should indicate the "readiness of schools" to provide young children and their families with experiences that contribute to successful learning. The background of the elementary schools and preschools whose principals and directors participated are presented. This is followed by the authors' validation and field test findings. Lastly, recommendations for revision of the "Schools Ready for Children" instrument and for further research are made. Similar information is presented for the assessment instrument dealing with children's characteristics and skills seen as necessary for successful learning experiences in kindergarten. (Contains 2 tables and 11 endnotes.)