A comment was left asking me to expound on Kayla's modifications - "who does them, how do they decide what to do, what's not enough, what's too much, and if having modifications takes her off diploma track."
The quick and easy answer to the diploma question is (unfortunately) yes: in this state having modifications takes the student off a diploma track. I blogged more about that in this post "G is for Graduating" To get a traditional diploma you have to have so many credits in core classes like ELA, Math, Science, Social Studies and to get those credits you have to pass those classes. Once you modify the curriculum the student isn't doing the same course work so they can't receive credit for it in the same way.
This link shows states that do and don't offer regular diplomas for students taking an Alternate Assessment based on Alternate Achievement Standards. SC does not offer a diploma for those students. I don't know if a student has modifications on their IEP if they can take the standardized tests or not - we were told they can have accommodations for standardized testing, but not modifications. But then there are some accommodations they can't have - ie in 3rd grade Kayla had an accommodation of tests being read aloud to her but they said that couldn't be done in standardized testing because it wouldn't accurately reflect her ELA scores. She also had 'use of a calculator' but we were told that accommodation couldn't be used in standardized testing until 5th, or maybe it was 6th, grade.
As I said in the linked 'Graduating' post - Kayla does need modifications; she can't do grade-level math without modifications. So at this point in time, unless things change, she isn't on a diploma track (even at her private school).
As for modifications and 'who does them'? Ideally it would be a corroborative effort between the special ed and general ed teachers with the special ed teacher providing most of the modifications (since modified work is what is basically being given in a self-contained classroom the sped teachers already have access to that type of curriculum).
I have a handout from a workshop I attended with a template that shows "What the class is working on" and "What Jane Doe is working on" (Pertaining to the same lesson the class is working on) and how s/he will access that lesson and participate in that lesson. We gave this template out a couple times at our IEP meetings but it was never utilized.
In the book From Disability to Possibility by Patrick Schwartz (highly recommend!) he suggests "Planning Time" be put in the IEP for the sped and gen ed teachers to meet once a week and go over what the next week's lessons are and how/where they need to be modified (another strategy we tried to get in the IEP, but couldn't).
How do they decide what to do? That is up to each teacher to decide what are the key points and vocab words they want the student to get from the lesson. Admittedly it is easier to modify assignments in Science/Social Studies than it is for a subject like Math.
Kayla's current Social Studies teacher (a former sped teacher) modifies her test by giving her 10 key items from that unit he wants her to focus on. In my post "Z is for Ziggurat" you can see how her test looked like - while the material on the test did come from her 6th grade textbook it wasn't as detailed or as much info as the rest of the students had on their test. Her test format is an accommodation by using simpler text and matching.
This teacher gave her another set of 10 study guide questions and this time the test was fill in the blank with a word bank. She also did a project on Egypt and where the students had to write 3 paragraphs on their project, she wrote 4 sentences.
SC is part of the National Center and State Collaborative (and the SC DOE just had training on this for their educators last month). This site is full of curriculum resources to be used in the gen ed classroom including instructional and curriculum resources for ELA and Math.