Alarm Clock Problems

I have been having alarm clock troubles since around December. About the time we started to have Jazz Band every instead of only twice a week. I would set my alarm the night before for 6:15(so I can press the snooze button a few times before I actually get out of bed). The next morning I'd hear a little knock on the door, and my dad would enter to tell me that it was 7 which is the time that Jazz Band starts. I would then proceed to either keep sleeping or get dressed quickly and go to school. This happened somewhere around three or four times in the month of December. My alarm clock troubles have continued into the New Year, and may be even worse than last year. Yesterday was Friday and on Friday school starts at 10. I usually get up at 9, so I can take my time and not have to rush to school like every other morning. At 10:48 my dad knocks on my bedroom to tell me it's almost 11. I couldn't believe, because I knew I set my alarm the night before. I remember setting it, because I almost forgot to do it. I somehow managed to sleep through the majority of my first period of the day. I didn't end up going to school until 1:45 that day, because we only have three periods on Friday. I only have two periods, so I just had to go to last class of the day. It was nice to be able to do that. I didn't even bother putting jeans. I just put on a pair of leggings and t-shirt, because I didn't see the point in wearing jeans for one class.