SO many variables wrote:
Are they all motivated? How old are they? What does their previous training look like? Are they coming off of cross?
Many coaches expect to win out of the box. It can take years to build a winner.
1. The thing that will lead to the highest peak is Aerobic Ability. Constantly try to increase the distance of the longer long run. A goal of 15-18 miles is good for a 4th year senior.
2. Sprint/speed development must be worked on all year long at least one day per week as it is the hardest thing to build in training
3. Speed Endurance is the most important things for these events but when do you put them in and how intense should they be. These are questions which must be asked for this is a thing that is usually over-done.
Recovery runs and days off are the most important. Even sprint/speed development days should have a recovery run the next day for you are working on the nervous system unlike other runs.