Self motivation in school?

Hello, I’m Kathy. I’m only 13, 14 in November. But I’ve been very slack and lazy since I started Secondary school. My attendance is around 85%, which, in my eyes is pretty appalling. I’ve been acting sick, which I feel truly ashamed of. At primary school, my standards were very high, but now I just can’t stop being lazy. I’m not naughty, I’d never misbehave or be rude to a teacher. However my work is of a low standard, and my punctuality is bad. It’s an ambition of mine to become a police officer, I’d love to make it into CID! To achieve that though I need to have good attendance and punctuality, good grades in most subjects. Do you have any tips to help me motivate myself before the Summer holidays end? Thank you.

First. Calm down. Take a deep breath. Relax. Look yourself in the mirror and say "I am totally cool, smart, and I have nothing to fret over." Upperclassmen can smell a "scared or nervous" freshman from a mile away and they might try to pick with you. Be confident and assertive at all times.
Stay Organized. Keep your notes, handouts, and other materials in a well organized manner. Being organized will help you make excellent grades and if your teachers are the type to take up notebooks for grading, they will really appreciate it. It also helps ease anxiety, and saves you alot of time.
Be yourself.
If you find any extracurricular activities you are interested in, by all means find out more information and try out for them. Don’t be scared. Now is your time to shine and do what you want to do. You will meet your best friends this way.
If you have plans to attend college, make sure that you start your high school career off right (3.3 at least-B+ average). If you find yourself struggling in any of your courses, tell your teacher or parents immediately so they can help you.
Have fun! High school memories last a life time.