I believe ALL STUDENTS CAN LEARN.  The biggest impediment to a students learning is themselves.  If they have all the passion and drive to learn but they do not have the knowledge or understanding of their needs, their style of learning and think of language learning as a rote process then they will never achieve success.  Knowledge of a language can be a means of survival or used as a tool to achieve your goals of success or be for pleasure to enhance social interactions in any sphere.  Whatever your goal....BE OPEN.  Mental blocks ARE real and placed there by ourselves because of our levels of discomfort in trying new things or feeling insecure or feel inadequate to the tasks we set ourselves.  There is NO place in language learning for this.  Expect to be pushed out of your comfort zones.  Expect to have to do more than what you would have liked in order to achieve your goal.  If you do not have an aptitude for learning languages then know that as long as you keep yourself OPEN, you will be able to achieve your goal through hard work.  Do not shy away from putting in the work to succeed. It is all to your benefit.