Many schools have an alumni event soon after graduation. The recently graduated students join in as new members of the alumni group.
Before the event, create a Collection with photos from each of the graduating years that will be represented. (If a drop-in, rather than an invitation event, just add from as many years as you can.)
Once the photos are added you can share in a variety of ways:
For quick access, create a QR code from the link for your photo presentation. Print out QR codes to put around the venue. Sharing this way rather than printing photos, means everybody has access to view and enjoy all the photos.