Dennis Walcott, in his first major policy address since taking over as schools chancellor, today outlined an aggressive plan to turn around the city’s troubled middle schools.

The plan includes closing struggling middle schools and opening 50 new middle schools over the next two years, both charter and district schools, Walcott said.

“If a school is failing its students, we will phase it out,” he said.

Walcott also said the city will apply for federal funding to radically overhaul 10 middle schools, a plan that includes dumping principals and at least half of the teachers at the targeted schools.