Struggling with decisions about my son's schooling

Regarding my 5th-grade son. He has moderate autism, a biting habit, throws tantrums with screaming fits when he makes mistakes or things don't go his way, is fixated on toddler shows, and puts things like his 4-year-old brother's building blocks in his mouth, etc... I think his mental age is around that of a preschooler. He's currently attending a special education class, but given how disruptive he was last year, people told me he should be recommended for a special education school. During this year's meeting, they said, 'He might barely make it in a special education class,' but I really don't feel like he'll be able to manage. However, if he goes to a special education school, he won't be considered a high school graduate and will be considered a junior high graduate. I was also explained that to get a high school diploma, he'd have to attend again later. He doesn't have significant delays in his studies. I don't know what to do for him...