The role of language and culture in large-scale assessment : a study of the 2009 Texas Assessment of Knowledge and Skills
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The inclusion of all students in large-scale assessment mandated by the No Child Left Behind (2003) requires that these large-scale assessments be developed to allow all students to show what they know, and that the results are comparable and equitable across diverse cultural and linguistic populations. This study examined the validity of the 5th grade 2009 Science Texas Assessment of Knowledge and Skills (TAKS) for diverse cultural and linguistic groups. The student groups considered for this study were selected based on all the possible combinations of three variables: ethnicity--White and Hispanic, test language--English and Spanish, and Limited English Proficiency (LEP) classification. Validity was assessed at the item and construct levels, and was analyzed from a psychometric, cultural and linguistic stance. At the item level, Differential Item Function (DIF) was conducted using the Mantel-Haenszel procedure. The presence of biased items was revealed for all pairwise group comparisons; with a high number of DIF items between groups which differed in English proficiency (approximately 50% of the test items), and a low number of DIF items between groups which only differ in ethnicity (approximately 15% of the test items). However, an analysis of the Item Characteristic Curves (ICCs), revealed that items classified by the Mantel-Haenszel procedure as advantaging the LEP groups, did so for students at low proficiency levels; while the advantage at high proficiency levels was for non-LEP groups. At the construct level, the structure of the English version of the TAKS was compared across three student groups using Confirmatory Factor Analysis with Multiple Groups. The hypothesized structure based on the TAKS blueprint, was rejected for the Group conformed by White, non-LEP students (MLM[subscript x]²[subscript(734)] = 1042.110; CFI= 0.845; RMSEA= 0.020); but, it was a good fit for Hispanic, non-LEP (MLM[subscript x]²[subscript(734)] = 819.356; CFI= 0.980; RMSEA= 0.011) and LEP (MLM[subscript x]²[subscript(734)] = 805.124; CFI= 0.985; RMSEA= 0.010) Groups. The results obtained from this study call to reinterpret the achievement gap observed in TAKS scores between the populations considered, and highlight the need for further development of guidelines that can better help to develop fair large-scale tests for all students.