I assume you've already looked at the relevant DOE advisements:
"33. If a student has a learning need based on a weakness or discrepancy, can it be included in a Gifted Individualized Education Plan? If so, where and how should it be noted?
The Gifted Individualized Education Plan is a strength-based document and if a learning need exists that stems from a student’s strength, it belongs in the Gifted Individualized Education Plan. The need(s) can be noted in the present levels and used to craft a goal/shortterm learning outcome, or it can be incorporated into the specially designed instruction. An example of a need based on a student’s strength might be support for long-term projects because he/she is working independently as part of a compaction opportunity. A child may need a learning contract developed to help chunk the project into intermediate steps with clear guidelines and expectations in order for resources to be secured ahead of time and allow the student the maximum opportunity to work independently. If a learning need does meet the definition of a disability and it is preventing the child from accessing the general education curriculum, then all needs, goals, short-term learning outcomes, specially designed instruction, and support services need to be addressed in one document, an individualized education plan according to the procedures in the Pennsylvania Code (22 Pa. Code Chapter 14). If the learning need stems from a student’s weakness and it is not a documented disability, it can be noted in the present levels section of the Gifted Individualized Education Plan, but it is not addressed in the goals, short-term learning outcomes, or specially-designed instruction. For instance, if a child struggles with organization and it is not connected to a disability or a medical diagnosis, it would be helpful for the Gifted Individualized Education Plan team to understand that aspect of a child’s learning. The team (consisting of general education and gifted education staff) will provide support in accordance with Pennsylvania Code (22 Pa. Code Chapter 4) through normal differentiation that would be offered to a child who struggles with organization and is not identified gifted. Therefore, since the support provided is not beyond the scope of the general education curriculum, there is no need to write it in a Gifted Individualized Education Plan as specially designed instruction."
It seems to me the most likely avenue that meets the statute would be to argue that his discrepant weaknesses in spelling and writing mechanics are limiting his access to appropriate programming and GIEP services for his identified above-grade level strengths in ELA (reading comprehension). That is, he demonstrates strength-based needs in ELA, based on his above-grade level reading, but placement into his strength-appropriate ELA settings is compromised by his discrepantly-low writing mechanics. Therefore, specially-designed instruction in writing mechanics is necessary in order to support his access to strength-appropriate ELA instruction.
If the school continues to claim that they are "working on it", it would be helpful to have them clarify the strategies and interventions they currently have in place, and how they are measuring progress (this is all relevant even for general ed supports), and also to specify if they are accommodating his writing mechanics in some way (which further supports the need for either formal accommodations going into middle school, such as one might find on a 504 plan, or skills remediation). E.g., perhaps they are not marking him down for spelling or other mechanics errors, because he is bright, cute and good.
