Thanks very much for letting me know.  I guess I thought sports pitches were so simple and obvious that it never occurred to me to look at the Wiki page for it.

That is an odd arrangement and I looked at it with a couple of different aerial photos before I was sure that what I was seeing really were the shadows of basketball backboards.  Some schools and parks have found unusual ways to find room for basketball hoops in cramped play areas.

I've only been using the landuse=recreation_ground this way for a couple of months now.  I saw that someone else had used this tag this way at another school in Texas (can't remember where now) and I thought it looked like a good idea.  This way, somebody with local knowledge can come along later and add a surface=* tag for the whole fenced area and not just the sports courts.  It doesn't hurt that it also looks nicer that way.