Bike question! I need help.?

I am 12 and live 3 miles from my school. Due to gas and exercise, I want to bike to school and to other places. On one street I go on the bike lane. What accessories should I get? (ex. water bottle holder, mirrors on helmet, etc.) Thanks for your help!

its more like 2.5 miles...

3 miles on bike is kind of far but its ok.

You definitely need a helmet. and be sure it fits, suits you well and that you ALWAYS wear it. I know you might here that a lot but lots of people have died because they got in a bike accident and weren't wearing their helmet.
Some people have little "bike fanny packs" where a little seat fanny pack is on the back of your seat but if you'll have a bag, then it won't be needed.
You should have a cargo carrying thing in the back( idk what its called). You attach it to the top of you back wheel and with some bungee ropes you can put your bag there, or a basket in the front but that's a little girly :D
You do need a water bottle holder because you definitely will get thirsty.
Mirrors aren't necessary because honestly, you can just turn but you can never be to safe.
BTW
Be prepared for biking almost every single day because 3 miles back and forth every day is a lot.
WEAR DEODORANT OR ANTIPERSPIRANT! because you might be late someday and be really fast but either your late or not, you need it. Antiperspirant is better because all deodorant has aluminum in it and can give you cancer and deodorant only takes the stink away, antiperspirant takes the stink and liquid away.

Hope this helped!

helmet, reflective stuff, cell phone, pump, lock, luggage rack.

3miles--i wouldn't worry about water bottle or mirrors.

ride on the right, in a straight line, with traffic, and remember most crashes occur at intersections--watch out for turning cars.

carry weight on the bike--not on your back, not on the handlebars.

A mirror, loud bell, a lime green vest for visibility and a lock/chain, rack for pack and of course a helmet.

Always leave early and take your time, avoid taking risks in traffic.

I did this when I was twelve, it worked out fine.

Don't ride when its raining heavy. Drivers cant see you and no one can stop.

do you have a shower at your gym. If its too hot you may sweat alot. I would take a change of clothes just in case. So you will need a rack on the back.