I have kids who are motivated and are pretty fluent in English. I can teach them easily and joke with them...they are an absolute joy. These kids took an oral test and most did great. I felt like a competent teacher and loved my job.
I have others who are quite nice, but know almost nothing. After studying English for a decade, they can not ask or answer a simple question. I gave these kids a really easy oral test and even gave them a short list of questions to study a week before the tests. Many could not answer questions you would ask elementary school kids. I felt demoralized. I must be the worst teacher.
I guess these are normal feelings for a teacher. I wish I knew this when I was a kid, I might have been nicer to mine.