The best thing to do is to start a healthy diet and exercise program with reasonable results. Healthy goal is about 2 lbs a week, anything more would be starvation which can led to worse problems. The easiest way to cut calories is to find alternatives to the unhealthy things that you drink and eat. Cut out the junk food completely, just a few snacks every once in a while. Cut out all soft drinks and DIET DRINKS, these are just as bad a regular non-diet sodas. Drink lots of water to flush out the body and keep well hydrated, this will result in gorgeous skin as well, distraction from a few extra lbs
ALSO, WEIGHT IS NOT AN ACCURATE MEASUREMENT, YOU SHOULD LOOK AT YOUR SIZE AS A MEANS OF CALCULATION. MUSCLES IS GOOD AND WEIGHS MORE THAN FAT!!!
Find some sport you like to play or bike/jog or something to add to your schedule to help you burn some calories.
Also, keep in mind that the clothes you wear can help hide a few extra lbs, look for sites that will show you what styles you need for your shapes. And a good confidant personality is the single most important thing to have regardless if your 20lbs or 2000! Look around not everyone is perfect, even actresses and models. Love and take care of yourself, immature kids only pick on people to make themselves feel better. If someone says your fat, then its probably because they think they are fat, or they are just trying to look cool. School is what is important, not the drama of high school or boyfriends.