Accommodations and Modifications 
1) A testing accommodation refers to a change in the procedures for administering an assessment. The accommodation is intended to reduce as much as possible the effect of a student’s special needs or limited English language proficiency on the assessment process so that the student is assessed on an equal footing with all other students. Testing accommodations do not change the kind of achievement being measured; they change how that achievement is measured. 
If chosen appropriately, accommodation will provide neither too much nor too little help to the student who receives it. 

2) A testing modification is a change in the procedures for administering a test that may affect the constructs being measured. For example, reading aloud those sections of the Reading test that students are expected to read independently represents a modification. 
A modification is sometimes necessary when an accommodation is not possible. A testing modification may lead to scores that differ in meaning between students who received the modification and those who did not receive it. The local, district or state policy usually determines whether these scores should be interpreted differently. 
For more information about Accommodations, seek out the "Directions for Administration" documentation for the appropriate test and grade level. This can be found in the Resources page of DataManager. Look for the topic "Accommodation and Modification"