I personally don't think that the wizard kid is dead. There are clues in the show that lead me to believe that he did some magic trick and lived before the car hit him.
Remember when Icicle spoke to the magician and told him he wasn't powerful enough for the wand and then the magician's kid on the bus stated that he felt his magic getting stronger? Pretty sure Stargirl is leading up to all the ISA parents either dying, coma, or going to jail. After that happens all of the kids will be left to fight amongst each other. And I think that the magician's son will try to kill Icicles to avenge his father's death.