Hi,
Not a naive question at all, and welcome to the community. The visual browser is a limited demo application right now, and doesn't provide browsing by grade level. In fact Learning Registry itself isn't designed as a search application, so doesn't provide simple filtering by grade level either. You can definitely write a "data service" to extract grade level and thereby provide filtering, but you have to decide which formats within LR you want to support (recommend Dublin core and variants as there's a lot of content in that format).
There is a forthcoming product currently funded by the Gates foundation called "Learning Registry Index" which will provide search/filter capabilities, and almost certainly will let you look at grade level, and it will definitely support curricular browsing.
LR is designed for international use and Australia and UK have been conducting research projects around LR.
For support of arbitrary curricular standards, I think most people will be using LRMI/
schema.org to describe their standards in LR (and elsewhere). LRMI permits arbitrary standards, so long as they have a unique identifier (ideally a de-referenceable URL to the standard). LRMI is the main mechanism I would foresee for mapping content to curriculum in LR and more broadly on the web.
So, not all the pieces are in place, but we should see quite a bit of new functionality over the next 3-6 months, so keep in touch. And where you have specific questions about data services or other functions, you should join the
LR developers group where you can get tech questions answered.
Sincerely,
Steve