I wonder what 'expelled' means anymore. When I was in high school, being expelled meant the end of your involvement with the public school system. It only happened to students age 16 and over (you could also drop out at age 16 under state law) and you were then on your own. I had several friends expelled (only one for taking a swing at a male teacher --- he missed) most often for truancy. If you were deemed 'incorrigible' under the age of 16, they sent you to "reform school" -- junior prison -- until you were 16.
I don't know how they handle this stuff today.
Im Milwaukee "expelled" means you get moved to another MPS school.