I'm a pretty tall high school kid and due to my lankiness, I have very long legs. This helps me considerably once I hit top speed because I have longer strides and therefore am a lot faster than shorter people. However I have trouble accelerating. Any suggestions on how to increase acceleration?

in my personal experience, hitting the weight room is the best way to increase acceleration. Squats, deadlifts, leg press etc. help a lot in my personal experience.

Good Luck!

jump roping is good for quickness

Check your running technique. A running coach can help you consideribly.

When you start out, you're first 6-8 steps are going to be shorter, quicker, until your stride increases to full lenght. THis will help you get going faster.