The Fire!Fire! Duel School is a school in Paradise City. Its advertisement can be seen throughout the city and features "Infernal Flame Emperor", "Firestorm Prominence" and "Spirit of Flames", with the background of "Molten Destruction". The advertisement can be seen in Den City as well.
Based on this school's name and sign, it seems that it teaches Duelists how to use FIRE monsters.
In Yu-Gi-Oh! VRAINS, Fire!Fire! Duel School sign can be seen when Skye Zaizen is walking in Den City.