Thank you for your post.
At this time, FileMaker Pro does not give you the ability to display the grouping field at the top of the page. One possible workaround is to include the grouping field in the Header. On the first page, include a Title Header that is blank so that it won't print the first grouping value twice. The caveat with this approach is if the grouping does break cleanly at a page break as that will print the new grouping on the next page along with the field in the Header.