How are the children assessed?

How are the children assessed?

How are children assessed and why do we use CITO tests?  
We are a Dutch Inspected Private B-3 School and are required to administer the Dutch CITO tests to all children over age 5. In addition, we do formal assessments in English twice a year.  This is based on the UK National requirements for students over the age of 6.
How do Winford Bilingual Amsterdam children perform on the CITO tests compared to other schools with  Dutch only programs?  
90% of children who have been with our programme continuously since the age of  4 have scored at above level in comparison to similarly aged children in Dutch only  programmes.   
75% of children who have not been in our programme from age 4 test at level when compared to similarly aged children in Dutch only programmes.
Summary of our assessments:
CITO from groups 2 to 8 (ages 5-11)
English testing from groups 3 to 8 (ages 3-11)