"Obedience is the primary object of all sound education." -Elizabeth Missing Sewell

What this quote is saying is that being obedient will help your education. For example: your teacher tells you too do your homework and if you don't listen it will affect your grade. If your teacher tells you too study for a test and you do, you might do good on that test. If your teacher to behave in class and you don't, it will affect your cooperation grade.