Your letters of recommendation should not just speak to your accomplishments, but also speak to the kind of person you are in an academic and extracurricular setting. Only a teacher who knows you well and has observed your performance in class can do that. It is best to select teachers who can add a qualitative dimension to your application and vouch for a student’s character, work habits, and potential. Different colleges will require a different number of letters of recommendation. However, most will ask for at least one teacher.