Several school districts in Georgia use two teacher-administered diagnostic assessments of student knowledge of mathematics as part of their multi-tiered system of support in grades K-8: the Global Strategy Stage (GloSS; New Zealand Ministry of Education, 2012) and the Individual Knowledge Assessment of Number (IKAN; New Zealand Ministry of Education, 2011), which comes in two formats (Counting Interview and Written Assessment). However, little is known about whether two teachers using the same assessment to assess the same student on two occasions within a short period of time assign the same Stage Score (interassessor reliability) or about how useful the teachers found the assessments (consequential validity). Rather than relying on occasional testimonials from the field, decisions about using diagnostic assessments across the state should be based on psychometric data from an external source. Districts not currently using the GloSS and IKAN assessments have indicated an interest in using them, if they are proven to be reliable and valid diagnostic assessments, to assess students' understanding of mathematics and determine appropriate levels of instruction and intervention. This study found adequate interassessor reliability for the GloSS and for the IKAN Counting Interview but not for the IKAN Written Assessment. The IKAN Written Assessment requires additional attention to improve training so that reliability can be established. Teachers indicated that they found the screening data from the GloSS and IKAN assessments more useful for guiding decisions about student instruction and intervention than the screening data currently employed. Although teachers in the study's focus groups expressed strong support for both assessments, teachers reported in the study's survey that the GloSS is more useful than the IKAN because it assesses students' solution strategies, unlike most other mathematics assessments. Teachers also expressed some criticisms of both assessments; for example, they believed that the GloSS should include vocabulary familiar to students and that the IKAN Written Assessment should be untimed. [For the appendixes, see ED607586; for the study snapshot, see ED607587.]

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