I have attended and led more eligibility meetings to determine if a student has a disability than I even want to think about. There isn't any "almost always" to it. Grades would be one factor among many that would be used to determine if a student has a learning disability.
Considerably more weight is usually given to formal academic achievement testing than to classroom grades in those discussions. I used to give the WIAT-II in a quiet room, one-on-one. The test was designed in such a way that most of the questions were on what I call the Goldilocks Level: not too difficult, not too easy, just right. Students very often performed much better on that test than they did in the classroom.
A statistically significant discrepancy in scores between two norm-referenced tests (the cognitive or IQ test and one or more areas of the academic assessment) would be a major factor in that decision. It was not the only factor. If there was no discrepancy, we would look at information from several sources to determine if there were an unexpected lack of progress or failure to respond to intervention. Honestly, that "back-door" option is often used to get someone into Special Education whose IQ is between average and mentally retarded, and it shouldn't be used that way. Special Education will not raise their IQ, only lower their expectations.
There are many, many causes for underachievement in school for gifted kids. It may be that your child recognizes--whether or not she can articulate it--the mismatch between her abilities and what she is being asked to do in the classroom. Adults complain about jumping through hoops at work, but kids hate it just as much.
Gifted kids with poor organization, planning, and executive functioning (and I am speaking from personal experience here) may never be challenged to develop those skills. When a big project comes along, they may be completely unprepared to plan and execute the project.
Gifted kids often try to keep a lid on their abilities in order to fit in. I used to count to three when the teacher asked a question, to give everybody else a fair chance. The teachers may have thought I just had a slow processing speed. I saw no point in getting good grades, because it would just make me stick out that much more. Gifted minorities often underachieve because they have a notion in their head that to do well in school is "acting white".
Girls sometimes hit a rough patch around puberty where their self-esteem and grades just tank. It might be for a few months, unless it becomes a permanent feature of how they think about themselves (I'm stupid!).
I could go on, but...
Last edited by Beckee; 06/16/12 11:43 AM.