Well Znix I can understand not feeling like you deserve detention, but me say this...once you get out in the real world and you start showing up late for work, there is no detention, but job termination aka "firing". What the teachers are trying to do now is not be mean but to "teach" you NOT to be late...not only just at school but anywhere.
Furthermore I learned a long time ago, that it's best to sleep with 2 alarm clocks, and 3 if needed. That way in case one goes off, you have more than 1 as a back up. You might sit and think "wait, why should I do that? The alarm clock "should go off"....yes it should...but will it? It's man made so it's guaranteed to fail.
That's like saying "I shouldn't have to drive with insurance because I'm a safe driver and I shouldn't or won't have an accident. Truth is no one can predict the future. That's why we buy insurance and sleep with 2 alarm clocks.
Now, I'll end with this...if and when you do come into late to school, you are late. It doesn't matter why you're late, you're late. Yes sometimes if you're always on time and you happen to have a flat tire, etc. and you call in, they'll forgive you. However I've seen it too many times happen...someone comes in late for one thing or another all the time....it gets old, they use up their "get out of jail free" cards....then they really do get a flat tire, etc...and call in, except they're told "I don't care if your tire is flat, if you're not in here by 7:30 am, YOU'RE LATE!
So you see the importance of being on time now?
Something to think about.