Progress in the validation of high stakes assessment: the case of Selection test for Nazarbayev Intellectual Schools in KazakhstanAugust 2, 201841st Annual Conference (2015), Dariya Kulbayeva, Frans Kamphuis, Frans Kleintjes, Miras Baimyrza, Nico Dieteren, Rustam Abilov, Zamira Rakhymbayeva