Describe a teacher who changed the way you study

The teacher I'd like to talk about is Mr. Rahman, who taught me chemistry in Class Eleven at a college in Mymensingh. Before I met him, my approach to studying was basically memorising everything the night before an exam, and honestly, it wasn't working very well. What made him different was that he refused to let us copy notes from the board. Instead, he would explain a reaction and then ask us to close our books and explain it back to the person next to us. At first I found this really awkward, because I realised I couldn't explain things I thought I knew. He used to say, "If you can't teach it, you haven't learned it yet." Gradually I started using the same method at home. I'd read a topic, put the book away, and try to explain it out loud to my younger sister, who was usually quite bored by it. The result was that my marks went up, but more importantly, I stopped panicking before exams. I still study this way now, and I think it will help a lot when I start university in Malaysia, where I'll be expected to work much more independently.