There's this one series I used to read that was called Nightmare Academy. It sounds cheese as heck, but it was REALLY good.

man oh man have you read Dragon Slippers? It was my favorite series as a child; i fuckin loved it

I haven't! Imma have to check that out!

Years ago there was a series called Replica about a girl who discovered she was a clone. It was awesome, way ahead of uts time. Also Animorphs.

Maybe I'll list predictable ones, but I just love them: Harry Potter, Artemis Fowl, literally everything written by Philip Pullman, The Lord of the Rings, A series of unfortunate events (so underrated!), Percy Jackson... I heard "Wonder" by RJ Palacio is cool, but I haven't read it yet.
There are other great authors, but it depens on the age. Oh no, that's rubbish! Here are other writers that I adored. Your childhood is somewhat flawed if you haven't read at least one book from Roald Dahl. Then there are Aidan Chambers, Jonathan Stroud, Eva Ibbotson, Meg Cabot, Joyce Carol Oates, Michael Hoeye... I could go on all day because reading is AWESOME.
Sorry for the neverending blahblahblah, here you are: http://s174.photobucket.com/user/april_rain_showers/media/potatokitten_zpsc231b366.jpg.html

Death Dealer for disturbed kids

There's another one I like called Heck: Where the Bad Kids Go. It's about Hell for kids, and it's really interesting.

Tamora Pierce is a wonderful young adult author with several different series. Fantasy type genre. I grew up with her books and they are just too lovely to not recommend.

Also, Chronicles of Nick by Sherilyn Kenyon

Ranger's Apprentice

The spider wick chronicles are really good!

Junie B. Jones & From the Files of Madison Finn ftw

may bird is a good series that has an eerie twist ( not too creepy for children though)