Need to know more

Coming to this topic, I was wondering about loads of things related to Japan.
1) What kind of desks to the schools have? Are they like the ones where you can open them from the top and store things inside or the ones that alow you to put things below?
2)And what's with the 'freshman' thing?
So...if you're a freshman, how old would you be then?
3)What kind of uniforms to Japanese policemen wear? I mean like...can someone describe it?
4)What's the diffrence of High School and Senior High School? Do they do the same things?
5)Is it a must to join the school clubs?
6) What kind of clubs are there in the school?
7) Is it possible to form your own club? If so, how to?
8) How to Japan celebrate X'mas?

Try an internet search for loads of answers to some of your questions. I Googled "Japanese police uniforms" and came up with whole pages dedicated to that topic in English, including pictures. The Princeton page seems good.

The same with "Christmas in Japan"- lots of pages with that title and detailed descriptions of what people do came up.

I can answer a couple questions but only according to my personal experience...
In the junior high schools and high schools at which I have worked, the desks have all been the type with a wooden 'box' on top of metal legs. The box does not open from the top, but rather has an opening on the side - the side facing the chair. Students slide their notebooks in from the side. Most of their belongings, they keep in lockers or cubicles at the back of the room, and they hang their gym bag/whatever from a hook hanging on the side of the desk.
I don't know what you mean by question #2. The Japanese high school (which I believe is the same as saying 'senior high school') has three years, 1st, 2nd, 3rd. The 1st year would equate to an american high school sophomore since the freshman-sophomore-junior-senior names are for four-year schools.
There are many clubs at the schools but I don't know if they are mandatory - I think they are highly recommended and 'the thing to do'. Someone who reads this forum has a son in high school and can probably answer the rest of the questions.