The California Commission on Teacher Credentialing extended a waiver Thursday that will allow those in teacher preparation programs to begin teaching while they finish required exams, coursework and practice hours. It was the latest in a series of state actions to ease teaching requirements during the Covid-19 pandemic. Since the pandemic began many teacher candidates — those who are in or have completed a teacher preparation program but have not yet earned a teaching credential — have been unable to complete required exams because testing centers were either closed or had a backlog of appointments due to social distancing requirements. Others have not been able to complete student teaching or required coursework because school campuses are closed.