This study was designed to investigate if the Batería Woodcock-Muñoz: Pruebas de Habilidad Cognitiva- Revisada is a valid cross-cultural tool to measure the cognitive ability students of three Spanish-speaking groups from two different Spanish-speaking countries. One group is represented by culturally diverse bilingual Spanish dominant students in Tucson, Arizona since there is an overrepresentation of bilingual students receiving special education services in all school districts in this area. The second group consists of monolingual Spanish-speakers from Costa Rica referred for special education. The third group constitutes monolingual Spanish speakers from Costa Rica performing at grade level.This research analyzed whether or not Memory for Sentences, a sub-test of Short Term Memory, Visual Integration and Picture Recognition sub-tests of Visual Processing in the Psycho-educational Batería Woodcock-Muñoz, is more difficult for the special education Spanish/bilingual population in Tucson than for the monolingual Spanish-speaking special education and grade level individuals in Costa Rica. Item p-value differences in each subtest were estimated and compared for all items for each subtest to detect if a major item difficulty order difference existed between Spanish-speaking groups that could be indicative of internal criteria of test bias. Results show that the item order of difficulty affects the tests' established cut off rules for both Costa Rican populations in the Memory for Sentences test, making it invalid for these populations; and that the Tucson sample group's performance is lower than that of both Costa Rican groups. In addition, both Visual Processing subtests are invalid for all groups compared since the item order of difficulty does not match the test item order, thus affecting the enforcement of the cut off rules and making these subtests invalid for these populations.Standardized assessments and intelligence trait are considered the results of mathematical and statistical expressions built on test developers' own cultural views and minds. They follow along the lines of the traditional reductionist assessment or scientific/medical models. As a result, it is concluded that bilingual populations will be at disadvantage because standardized assessment neither links assessment to familiar language, cultural relevant information, and experiences nor considers how the bilingual mind processes information.