The Boxcar Children was the first book I loved. My second-grade teacher read it to our class and I could hardly wait to get to school each day to find out what happened. It was pure magic for me.
My favorite book for middle-school students is Among the Hidden by Margaret Haddix. Set it the future, Luke is forced to hide upstairs because his parents broke a criminal law by having a third child. If Luke is discovered by the Population Police, he will be killed, so he hides in the attic while his two brothers attend school and have normal lives. One day, when his parents are at work and his brothers at school, Luke sees a girl's face in the window of a home that already has two children. He knows he's found another person like himself. This book will make you keep turning the pages until you find out what happens when Luke dares to slip out and meet the other "shadow child."
My favorite Y/A book is Snow Bound by Marry Mazer. Set in upstate New York, two teenagers meet and are forced to survive a blizzard together. These two total strangers, who don't even like each other very much, finally realize their lives are at stake and they must cooperate to survive. It makes you cold to read this book, but you won't want to put it down.
Of course, my first mystery, Why Johnny Died, is also a great book for high school students and has been used in several high schools. Read it and find out what really happened to Johnny Benson and why the school administrators covered it up. If you do read it, I'd love to hear from you!