What are the potential benefits and challenges of online statewide assessments for students with specific learning disabilities? And what information should the general education teacher be prepared to share with the student's Admission, Review, and Dismissal (ARD) committee?

I was a certified special needs teacher for K-12 and was responsible for testing special needs students while working in a Title I public school system. I will share with you some observations from my professional experience in response to your question.
Assessing students on a computer is a very different thing than the traditional paper-and-pencil assessment. The preparation for a high-stakes assessment is very time-consuming and can be extremely detrimental to a student's academic confidence level. A student with a disability is, in many ways, more susceptible to stress and the pressure to do well on high-stakes assessments.
In all states, due to federal law, students will have specific accommodations (extra time, equipment, parts of the assessment may be read to them, etc.). These may or may not be helpful to students. One critical aspect is that, in the classroom, the accommodations for students with disabilities have to be followed on all assessments. The fidelity as well as practicality of this instructional practice often conflicts with high-stakes assessment. Students with disabilities are required to take the same exam under the same conditions as other students. The assessment is not changed due to a learning disability.
One possible example is a fifth-grade student with a reading comprehension level of a first-grade student; this student is still expected to perform at the same level as other fifth-grade students. The preparation for the exam is not on the student's reading level. Instead, the student is prepared by working on fifth-grade reading comprehension level material. Immediately, the conflict becomes apparent. Teachers want to see the student's reading comprehension proficiency increase.
In this example, if by the end of the year, this student rose in reading comprehension ability from first to a third-grade level, that is a significant gain. State assessments are not calibrated or reported to reward this student for their academic work. This is one example of how online assessments can prove to be detrimental to a student if not presented in the proper context. Online assessments compound the problem in several ways.
Think about how you personally read a page of written material from a magazine or book. If you are the average reader, you may use a highlighter to shade essential points. Possibly you take notes or use a graphic organizer to make notes about the material. The entire page is in front of you, and if there are multiple pages, you can place one page next to the other to compare the texts.
Think about a computer screen. How big is the screen? Many states test their students on laptops, I-pads, or Chrome Books with small screens. Does all the page material fit on the screen? Can you make notes on a graphic organizer or highlight materials? Is a side by side page comparison available? While it is true that some online assessments allow students to highlight and have a place for notes, using these tools for a student with a disability is more of a distraction than a help.
What about students that have a disability that requires parts of the test be read aloud? The technology reads the material to them. The problem is the reader does not have a natural sounding voice. In many observations of students being read to, after a few minutes, the students begin to click answers without hearing all of the material. The assessor or proctor has no way of knowing which student is not listening to all the content as they are probably monitoring between eight and fifteen students all wearing headphones.
And what happens when the wifi goes out or the computer glitches? Many school districts do not have the bandwidth or the appropriate technology to assess students without interruption. For a student with special needs, any distraction can be frustrating and throw the student off track. The same is true for regular education students. These are just a few of the problematic technology problems.
In preparing students for online testing, a teacher needs to be fully aware of the potential technical problems and have a plan to deal with them. Students should practice what happens if a computer goes blank or if there is some interruption. Teachers should take a practice exam or a similar exam on the equipment the district is planning to use for the students to take the assessment. This is the only way you can prepare your students for things like the page not fitting on the screen. The student will have to scroll down, and the teacher has to teach the student how to manipulate the tools to navigate the material on the screen. There is a big difference in taking a test on a seventeen-inch monitor than taking the same test on a ten-inch I-pad. Providing a practice session with the students so they can use the tools is essential. Lighting and seating are critical issues. You can't wait until the day before the test to run a practice.
As part of the general education teacher's responsibility, a teacher should request every available accommodation allowable under the student's IEP. The request should be in writing on the first few weeks of school. Students should take the mock assessment, and the teacher should observe how the students perform. Interruptions should be part of one of the mock assessments. All of the observations should be made part of the student record during ARD meeting and with parents.
States have decided to use online testing for several practical reasons. It is obviously less expensive than paper, results come back much quicker, and online testing eliminates the problem of how some teachers read the instructions to students and how they manage students during the test session. The question is, if the assessment is designed to measure a student's academic proficiency, then does the disparity from district to district, school to school, and classroom to classroom in technology and technical skill impact the achievement score on an assessment?
While technology is excellent for the economics of standardized testing, is technology also beneficial to students for high-stakes assessment? For the most vulnerable of students those with disabilities, how does technology make the test more equitable? These and many more questions need answers as online testing becomes the norm.
https://elearningindustry.com/15-benefits-of-computer-based-testing

https://www.fairtest.org/standardized-testing-and-students-disabilities