http://www.highlandstore.com/acatalog/Kids.html

kids kilts as shown here and the next picture have the apron opening on left. But it looks like the lad has kilt pin on right.

If I was making one for a boy though - I would make it so it opened to the right.

As a general comment-you see many women wearing mens kilts (open right) I have never seen a man wear a ladies kilt (Open Left)