The kids have so much stuff related to school to organize!
In their closets, I keep their monthly calendars. They have their own calendar with all their activities on it. I also tack a sheet protector in their closet and change out their monthly school calendars from their teachers. This allows them to know what is going on that day and allows me to know if they need specific clothes (For example, my son's preschool does color day. So, I can look at the calendar in his closet and remember we need a yellow shirt that day!)
For journals, artwork, and other papers that come home from school, I have a "banker's box". I put everything that comes home on top of the box and then later go through it to see what is worthy of keeping. I don't keep everything - it's TOO much! If it is special, sentimental, or a good example of their capabilities, then I keep it and file it away in the box. I got the big file folders (& the banker's box) at Walmart. I labeled the folders according to occasion because I like to display their artwork during the holidays and it's nice to already have it sorted by holiday/occasion. But, you could also label the folders by grade. On the back of the keeper item, I put their name and date and file it away.
In my laundry room, I have all my items that I need to keep handy. This is a good place for us because it is right by the kitchen and the door we leave through. I have an information station with a dry erase board, a calendar, the kids' school day schedules, important phone numbers (good for the babysitter), and the cafeteria menu for the month (also in a sheet protector tacked to the wall). On a cart, I keep their lunchboxes, backpacks, and other handy items. The other handy items include empty bags, an activity bag that we take to restaurants (with games, markers, etc.), clorox wipes, a cup with scissors/sharpie/pen, brush, sunscreen, hand sanitizer, and lint roller. I also use the cart to collect any items I need to send into school so I don't forget them! There are hooks hung above the cart for fleece pullovers and coats in the winter too.