It’s not clear why he couldn’t get up to algebra 2 starting with algebra 1 as a freshman? The typical sequence is Alg 1, Geo, Alg 2, Pre Calc. When I went to high school, I doubled up Alg 1 and Geo the same year to get through Calc because I couldn’t take it sooner.
I’m have a BS math major and I tutor math for high school students. If he is struggling, I would not rely on summer tutoring to push ahead. It’s much better to have the concepts really cemented. Math skills are often developmental and that “click” may happen at different ages for different people. It’s why some adults returning to school suddenly find getting through math at a CC not a problem on their 2nd go around after struggling heavily the first time. Who knows? He might be lighting the world on fire with his math skills in a year or two.
That said, they may not click for others. Has he been evaluated for learning disorders? Dyscalculia is a common diagnosis in kids that struggle with number operations.
I might use some summer tutoring to cement pre-algebra skills. Maybe some out of the box problem solving to really cement the concepts. A tutor that is very hands on with demonstrating concepts visually may be helpful? That seems like a better use of time for a kid barely getting through 8th grade math with special ed teacher helping.
No matter what happens, your child can go to college if he wants and has options.