Lets be realistic here.
It takes a few minutes every morning, and its a good indicator when people are late.
Rather than going "oh, its inconvenient for when people are late" how about "its a good way to show what people are late"
Being late isn't a character trait, its a character flaw and its one thing schools should teach people to overcome so they can succeed in life. Reading, Writing and Math don't really do much good if you are just going to sit on welfare your whole life anyways since you can get your ass to work on time.
How about the fact that it instills civic pride, and a feeling of patriotism, which leads to better adherance to the laws.
We sing the anthem at hockey games, we can spend the damn 2 minutes to start the morning singing the anthem.
Hell, why bother teaching them anything, lets forget history class. What good is knowing the nations history if you don't really care about the nation anyways?