A vocational school will have to keep looking for a bigger home now that the City Council here has denied the use permit it needed to move into offices along a thoroughfare dominated by auto dealerships. Antioch council members voted 4-to-1 Tuesday to overturn the planning commission's approval of a conditional use permit for Contra Costa Medical Career College, citing the need to reserve the site on Auto Center Drive for the kind of businesses that can produce significant sales tax revenue.