Particularly popular in the younger grades (preschool to elementary), but sometimes available all the way up to high school, Montessori schools offer an alternative vision to the standard lesson format of most classrooms. Instead of listening to whole-class lessons, Montessori classrooms allow students to choose which "tasks" or activities interest them. These tasks centre around special Montessori puzzles - their essential feature being they contain a right answer and allow for selfcorrection. A strong emphasis is therefore placed on lessons being concrete and rooted in practical experience, along with students developing a sense of self-sufficiency, confidence and curiosity.