With badly blistered feet, I was able to walk about 25km per day. That may help you gauge how far you can cover (remember, you cannot walk faster than your slowest member).
No one can walk from Roncevalles or Pamplona to Santiago in 16 days (unless you and all of your students are all superb athletes and no one gets foot or leg problems--supremely unlikely). So you have to either start closer, or take buses through various sections. I've posted elsewhere my itinerary for a shortened Camino that skips the urban areas and a dangerous bit of road walking after Villafrance de Bierzo, but even that is, at best, three weeks, not 16 days.
As Falcon269 said, Leon could work as a starting point if you are going to end in Santiago (I'd still skip the walk into and out of Pomferrada; and I would not want to risk students I'm responsible for on that road between Trabadelo and Los Herrerias) . If you are going to end in Finisterre, you might start closer (say O Cebreiro).
Alternatively, you could just walk the mountain sections (SJPP to Pamplona, then pick up again at Los Herrerias), or sort of put together your own sampler. Say some mountains, Roncevalles to Pamplona, some of the rolling hills of Navarro and Riojas, a few days on the Meseta, and then the last 100km from Sarria.
Better yet--I'd get your students involved in this discussion. What do they want to see? The various geographic areas described above; various UNESCO sites like Yuso and Suso (ancient monestaries where Spanish was first written down) and Atapuerca (earlies humans in Europe); various architectural monuments (the cathedrals in Burgos, Leon, Gaudi's Bishop's Palace in Astorga); various feast days in certain towns and villages (you are too early for San Fermin, but every town and village has their own feast day celebrations and traditions). Also, the student's studies might influence this (are they anthropologists, architects, linguists, etc.).
Bottom line: with 16 days, you are going to have to get selective, which means that you are going to need a serious discussion about what criteria you want to select for. When you have that criteria, write back and tell us, and we'll try to make suggestions helpful based on that criteria.
Welcome to the Camino.