Families for Excellent Schools, a charter-schools organization known for its battles with Mayor Bill de Blasio and its close relationship with Eva S. Moskowitz, the mayor’s frequent antagonist and head of the city’s largest charter school network, Success Academy, said on Monday that it was shutting down. The organization announced last week that it was firing Jeremiah Kittredge, its chief executive officer, after an accusation of “inappropriate behavior toward a non-employee.” But the decision to close seemed to reflect financial problems rather than the loss of a single employee. Families for Excellent Schools for years was the well-funded face of the charter school movement in New York, but its support seems to have evaporated. In fiscal year 2016, the organization reported revenue of more than $19 million and expenses of more than $20 million. Its website lists 40 employees.