As Florida prepares for the arrival of medical marijuana, the Miami-Dade School Board is urging lawmakers to keep cannabis away from school children — unless they have a prescription. At a meeting on Wednesday, the board voted unanimously to call on the Florida Legislature to ban medical marijuana dispensaries within 2,500 feet of schools if they sell anything other than the drug, such as pipes and other paraphernalia, and to prohibit medical marijuana products made to look like candy.