Somehow, there's often something of major importance wrong in children's rooms.

Usually it's floor space - these rooms tend to be the poor relatives in the space family. Often it's badly placed windows or too small a closet. And occasionally, it's all these problems combined and no wall space as well.

All of the above was the case in a recent room I worked on. This was particularly unfortunate because the teen-age boy who lived there not only needed space for his stereo and records and tapes, but also he needed storage space for books and a big space for his homework. But his folks pointed out early in the meeting that they were going to be moving to another city in a couple of years and didn't want to do anything "built-in" that wasn't totally portable.

After shuffling the bed and bureau and chair in as many different combinations as possible, I came up with a plan that give me a free corner between two windows set at right angles to each other. The corner was too small for the bed, which would have had to be placed under one or the other of the windows. Since the house was old, there was no way to keep out drafts and this wouldn't have been cozy.

But the corner worked perfectly as a study area. To make the storage I designed four rectangular boxes of stock 12-inch lumber. Each box was 42 inches long, one foot deep and one foot high. Inside, the boxes were divided with vertical spacers. The spacers also acted as reinforcements to keep the wood from warping or sagging under the weight of books or other heavies.

I painted the boxes gloss white throughout and then hung them from L-shaped brackets on the wall in the corner between the windows. The boxes begin at the top of the window frame and continue down. They are staggered from one side to the other, making four-feet-by-four-feet of storage space.

In another home, the box units could be used side-by-side on a long wall as a kind of buffet or credenza. They could be stacked one on top of the other, leaving as much space between them as necessary, to fill a single space from floor to ceiling. Or they could be placed on casters and used as tables. Or they could be hung under windowsills to make storage out of the throw-away space below the window.

Under the box units is a four-foot-long work table, just a plain Parsons' table with a white plastic laminate surface. On the underside of the table, I hung one more box unit, this one a single, one-foot cube. I painted this orange-red on all sides, to match the orange-red of the Venetian blinds in the windows.

In lining the boxes up with the top of the window frame, I was using the windows as a design reference. The windows were eight feet above the floor, leaving plenty of space between the top of the desk and the bottom of the first box unit. If you were doing this in a conventional house with seven-foot high windows, you could simply start the first box at the ceiling or make the boxes lower.

A posture chair with a seat and back in the same dark green as the walls makes a handsome and practical background for this corner strategy.