High School is a piece of cake. When I was going into the 9th grade I was nervous. However, once you get into the work of things it really is quite fun. I have much more fun at High School than I ever did in Middle School. Of course we were all afraid of swirlies but that rarely happens
Don't worry, the first day or two may be nerve racking but after that it is a breeze. Make sure you make plenty of friends...friends=good.
The work doesn't get much harder (IMO) but I guess it depends on what school you go to. You are expected to be more responsible in High School so say goodbye to late work. At my High School teachers do not accept any work that is late.
Basically if you try to enjoy it and not dread it than things will be great but if you worry about it than it only makes things tougher. Good Luck and enjoy your High School careers.