In many cases, students who were assessed as being low in both ability and achievement did not qualify for special education services unless they had a cognitive delay. what are two of the difficulties involved in this process?

Over-reliance on IQ measure and requirement to wait for the discrepancy between IQ and achievement.  

Explanation:

The discrepancy between IQ and achievement is a traditional method used to determine whether the students have a learning disability and need special education services. This model is based on the concepts of the normal curve. This model assesses whether a consequential difference or difference exists between students' scores on an individualized test on general intelligence and his sore obtained from one or more academics achievements. But there is some limitation of this model as it doesn't measure the quality of students. Some students may be identified as the disability when in realities they simply have not experienced classroom instructions that meet their learning needs.