Reexamining English only in the ESL classroom

"The more students exposed to the language the more quickly they will learn" I believe in the previous statement, but I am not against bilingualism in the classroom. Since the purpose for the students to study in the ESL institution is to learn English a better way, I strongly recommend using English alone in the classroom unless the students could not understand the lesson without understand some words in their L1. When I was in England last year, the principle strongly believed that the only mean to learn English was through speaking it all the time. He used to be angry when he noticed some Spanish spoke in their L1. I told myself that I will use this way when I came back to my country. I encouraged my students to speak English if they are in the classroom and nothing more than English. I succeeded but the problem was some students tried not to participate because talking in English all the time in class limited their ability to speak. I found that some students had something in their mind but they could not say it in English. Finally, I told them that I would speak in English all the time unless you did understand and you had the chance to speak in English unless you had something difficult to say and you would like me and the students to help.