They use new practices and ideas invented by others and themselves. Teachers use those new practices to bring about more student involvement. The students participate more. Teachers foster student responsibility. It's easy for students to get lost in a crowd.
Teachers increase the number of tasks assigned to each student.
The students are given more practice. Teachers change their questioning technique. They increase the discussion of ideas and bring about more understanding. Teachers spend more time on laboratory work and demonstrations. Practical application of skills is stressed.