If the minor is not a party to the Administration for Children's Services (ACS) case, it is odd that the minor has a lawyer; the lawyer probably means that the court cannot order a non-party to take the test.
However, as a matter of parental discipline, the parents can instruct their child to take a drug test. If he refuses, they can impose any punishment allowed by law, including grounding him, taking the door off of his bedroom, and leaving his room equipped with a mattress, sheets, and a couple of embarrassingly ugly jumpsuits for him to wear when he goes out. So... as they say, pick your battles wisely.
Also, if it isn't obvious to the minor and his lawyer, the court is going to figure out that the child is using drugs -- and that may inspire the court to initiate juvenile proceedings through which the child could be court-ordered to submit to drug tests.

