MIAMI — Since the start of the 2022-23 school year, nearly 10,000 students from Cuba, Haiti, Nicaragua and Venezuela have enrolled in Miami-Dade County public schools — about 2,500 more students than who arrived in the entire 2021-22 year, reflecting the surge of immigrants coming from those four countries over nearly six months. All told, the district has enrolled more than 14,700 new students who’ve emigrated from another country, an unexpected wave that comes at a time when the district is grappling with an already thin workforce and classroom teacher vacancies — one of the pandemic’s linge…