The data were collected between 1999 and 2013 as part of the Netherlands Twin Register (NTR)'s annual teacher survey. The data collection for the teacher surveys is ongoing and each year, the parents of children that are approximately 7, 9 (before 2009 10 years old) and 12 years old are contacted to ask for their permission to approach the teacher(s) of their children.The survey for the primary school teachers includes limited information on the teacher, class and school, items on adaptive functioning of the child at school, the Teacher report Form (TRF) (Achenbach, 2009; Verhulst & van der Ende, 2004) and the short version of the Conners’ Teacher Ratings Scale - Revised (CTRS-R) (Conners et al., 1998; Conners, 2001).The survey data are stored in harmonized databases organized by age at the time of data collection. Since the CTRS-R data was collected separately from the rest of the teacher survey until 2006, it is stored in a separate database.In EASY, the databases from for the different age versions of TRF and CTRS-R can be linked through anonymous identification numbers. Please consult the data manual (DocumentationDataCollectionTRF_NTR.pdf) for more information about the data collection and the relationships between the datasets from the NTR teacher survey