A parent sees a grade-limited product only if at least one of their students is in one of the product's grades for the current school year. For example, a product limited to grades 1 and 2 is shown to a parent with a 2nd grader, but not to a parent whose only student is in 4th grade. Students are treated the same way: a student sees a grade-limited product only if they are in one of the product's grades. Products with no grades selected are shown to everyone.
The same grade limits apply to the products included in the weekly newsletter, so parents and students only see the newsletter products that are meant for them. This is true even for parents who are store managers or admins.
In the store, everyone else — store managers, admins, teachers, and staff — sees every product, regardless of the grades selected. That way, store managers can always review and test grade-limited products, even if they don't have a student in those grades. Teachers and staff also see every product in the weekly newsletter.
Products shown on the registration page are shown there to everyone, so keep that in mind when choosing that option for a grade-limited product.