Controlled Drawing Observation (CDO) was developed by Tove Krogh and it has been used in Denmark, Finland and Estonia for assessing a child's readiness for school. CDO is a group test, it gives information about a child's functioning in an educational setting and it serves as a starting point for later individual assessment. The goal of the study was to examine the suitability of CDO for assessing a child's readiness for school and predicting school achievement during the transition period from kindergarten to school in Estonia. A total of 112 children were studied longitudinally at two points in time. Forward-stepwise multiple regression analysis showed that results of CDO predict a child's success in mathematics and the Estonian language at the end of the first grade better than teacher reports and the results of individual tests. (Contains 5 tables.)