Recitals are an important part of development on the violin. Not only do they allow a musician to prepare a piece to a high level, but they also allow the student to perform for others. I do not believe that we should study the violin if we never perform for others.
Recitals should be character building, however, it should should not be a time where a student falls on their face. If there is any chance of that, a difference piece should be selected. One bad experience on stage can lead to years of agony when preparing for recitals. I try to make sure all students are successful in their endeavors of playing solos in front of others.
With older students, you should be especially cautious. I try to pick pieces that will build tone or technique, but not overextend a student. Older students may work for up to a year on a solo piece. These are pieces that increase their understanding of the instrument. Smaller pieces should be kept while playing large ones in order to allow backups for recital time.
An expectation of having to play in a recital is one of the most motivating things for young instrumentalist. If your students don’t perform in front of each other each semester, I urge you to make it a tradition. It is worth the time and energy it takes to prepare for such events.