Candice Foster said the attack occurred Wednesday after her 15-year-old son, Micheal Boutcher, missed the bus home from Flint Northern High School.
Boutcher has been diagnosed with Asperger syndrome and attention deficit hyperactivity disorder.
Boutcher said he asked other students how to get home. One offered him the marijuana. When Boutcher refused, two boys began to hit him.
A man living nearby came to his aid and drove Boutcher home.
Foster said her son attends Flint Northern because Southwestern High School doesn't offer his special-needs classes. Still, she said he will now attend Southwestern.