When preparing students for individual recitals, I think it is important to pick a piece they are familiar with at least one month before the recital. They should have plenty of opportunities to polish the piece before performing it in front of others. Some of the ways I like to prepare are letting the student perform it independently in lessons as many times as they can before the recital. I also like to play harmony parts on my violin. I have found playing with the students too often does not allow them to learn to play independently enough for recitals.
Some teacher suggest 100 polished performances of a piece before the recital. I do not completely agree with this, but I think stressing several polished performances over a number of weeks is best. I think extracting the preview spots is also a good idea.
Another idea is to have a coloring page with several small spaces for them to color each time they have a polished performance of the piece. Maybe they could perform it for 30 people before the recital. (Neighbors, pastors, friends, relatives, teachers, principals, or whoever.)