RTL support in a child theme

I have a site that is tri-lingual (English, French and Arabic). When using the twentytwelve theme, on the Arabic version, the sidebar moves to the right which is the correct thing to do.

However, now that I’ve created a child theme the sidebar no longer moves to the left, but stays on the right in the Arabic version of the site.

I tried adding RTL support in the child theme’s style sheet, but that just aligned all the LTR text to the right.

The site uses WPML for multi-lingualism. So I may have to refer to them in the end, but I thought I’d check here first.

Thanks.