This study used multilevel measurement modeling to examine the differential difficulties of math and reading items for Grade 6 students participating in Ontario’s provincial assessment in 2005-2006, in relation to whether they received a setting accommodation, had a learning disability (LD), and spoke a language in addition to English. Both differences in difficulty between groups of students for all items (impact) and for individual items (differential item functioning) were examined. Students’ language backgrounds (whether they spoke a language in addition to English) were not significantly related to item difficulty. Compared to non-accommodated students with LD, math and reading items were relatively difficult for accommodated students with LD. Moreover, the difference in overall impact on math items was larger than on reading items for accommodated and non-accommodated students with LD. Overall, students without LD and who did not receive a setting accommodation outperformed students with LD and/or who received a setting accommodation as well as accommodated students without LD. It is important to note that, because this was an operational test administration, students were assigned to receive accommodations by their schools based on their individual needs. It is, therefore, not possible to separate the effect of the setting accommodation on item difficulty from the effects of other differences between the accommodated and non-accommodated groups. The differences in math and reading item difficulties between accommodated and non-accommodated students with LD may be due in part to factors such as comorbidity of LD and attention deficit hyperactivity disorder (ADHD) or a possible mismatch between the setting accommodation and the areas of disabilities. Moreover, the results of the present study support the underarousal/optimal stimulation hypothesis instead of the premise of the inhibitory control and attention for the use of setting accommodation. After controlling for the impact across all items of setting accommodation and LD, several math and reading items were found to exhibit differential item functioning (DIF). The possible sources of DIF were (1) math items that were not adherent to specific item-writing rules and (2) reading items targeting different types of comprehension. This study also found that the linguistic features of math items (total words, total sentences, average word length, monosyllabic words for math) and reading items (word frequency, average sentence length, and average words per sentence for reading) were associated with math and reading item difficulties for students with different characteristics. The total sentences and average word length in a math item as well as total words in a reading item significantly predicted the achievement gap between groups. Therefore, the linguistic features should be taken into account when assessments are developed and validated for examinees with varied characteristics.

This study used multilevel measurement modeling to examine the differential difficulties of math and reading items for Grade 6 students participating in Ontario’s provincial assessment in 2005-2006, in relation to whether they received a setting accommodation, had a learning disability (LD), and spoke a language in addition to English. Both differences in difficulty between groups of students for all items (impact) and for individual items (differential item functioning) were examined. Students’ language backgrounds (whether they spoke a language in addition to English) were not significantly related to item difficulty. Compared to non-accommodated students with LD, math and reading items were relatively difficult for accommodated students with LD. Moreover, the difference in overall impact on math items was larger than on reading items for accommodated and non-accommodated students with LD. Overall, students without LD and who did not receive a setting accommodation outperformed students with LD and/or who received a setting accommodation as well as accommodated students without LD. It is important to note that, because this was an operational test administration, students were assigned to receive accommodations by their schools based on their individual needs. It is, therefore, not possible to separate the effect of the setting accommodation on item difficulty from the effects of other differences between the accommodated and non-accommodated groups. The differences in math and reading item difficulties between accommodated and non-accommodated students with LD may be due in part to factors such as comorbidity of LD and attention deficit hyperactivity disorder (ADHD) or a possible mismatch between the setting accommodation and the areas of disabilities. Moreover, the results of the present study support the underarousal/optimal stimulation hypothesis instead of the premise of the inhibitory control and attention for the use of setting accommodation. After controlling for the impact across all items of setting accommodation and LD, several math and reading items were found to exhibit differential item functioning (DIF). The possible sources of DIF were (1) math items that were not adherent to specific item-writing rules and (2) reading items targeting different types of comprehension. This study also found that the linguistic features of math items (total words, total sentences, average word length, monosyllabic words for math) and reading items (word frequency, average sentence length, and average words per sentence for reading) were associated with math and reading item difficulties for students with different characteristics. The total sentences and average word length in a math item as well as total words in a reading item significantly predicted the achievement gap between groups. Therefore, the linguistic features should be taken into account when assessments are developed and validated for examinees with varied characteristics.