If the child makes minimal choices, a beginners self-determination plan should be instated. To create a plan for the child, identify parts of the day in which a choice can be made. Loose some of the rigidness of the daily routine to allow for choice-making.
In the morning the child can choose where he wants to hang his coat.
As a high schooler, he should be encouraged to buy his snack from the machine so he may choose. If he brings a snack from home, ask the family to include two so he may choose which one.
He may help arrange his task schedule for the day.
After making any of the choices he should be held to those decisions and not allowed to swap. This will teach the child the consequence or rewards of his decisions.