In nearly every job or position you hold during your time in the United States will require you to be punctual, which means being on time. This practice will serve you well in both your academic and professional careers. Being punctual is possibly the single, most important thing for any job you may have. It is something that most employers expect from their employees, and it is also what many professors expect from their students.
Nothing disrupts a class more than a latecomer who habitually comes into the classroom late. Coming in 5 to 10 minutes late draws attention to the person coming in late, and interrupts the teacher who is trying to conduct a lesson. It also disturbs students who are concentrating on the professor's lecture. Being late is rude and looked down upon in American society. It also serves as a disadvantage to the person coming in late. If a student arrives 10 minutes late, he or she may miss an assignment, or roll call. Roll is called generally at the beginning of a class to see who is present and who is not. It also can indicate who comes in late to class. You don't want to get the bad reputation of always coming in late to class. So leave home a few minutes earlier to ensure you won't miss any class time. It is a good habit to get into because punctuality is important in the workforce.
Generally speaking, most employers set specific times for their employees to arrive to the workplace. Normally the workplace is in an office or factory, but sometimes could be at a remote location. Regardless of where your particular workplace is, it is important to arrive on time, or preferably a few minutes early. This shows your employer that you are a good employee who can be counted on to be at work. So be on time, and you will benefit greatly from this.