I interviewed a veteran high school Science and Math teacher. Standards are means of determining what a thing should be. They are used by school districts and individual schools to guide teachers and define what is expected of the students to learn in a particular subject.
Standards are necessary in public school setting.
Standards focus on, limit and define what is expected to be learned by students in a certain subject. Standards define what is to be taught , but not how topics are taught. It depends on the subject , and on what topic within a certain subject. A teacher must use one or more specific assessment method for each topic or activity. Assessment can be done by observation, by examining and critiquing a portfolio, by multiple choice, matching or essay questions, by assessing the performance of students in certain task, by quizzes , by discussion and by standardized test.