Coaching dilema

OK, I'm back feeling more inspired. Wednesday morning I took the top group of Mountbatten students out running. All six highly motivated, no moaning about the cold or how far we were going, they just got on with it. We did a couple of miles interspersed with 3x100m sprint (15 second recovery) and a sprint up Seward rise. Finished the run with some Indian file, sprint to the front work.
Coaching a group like this is easy and fun, but a philosophical question, where should I invest my coaching effort?

With the top group who respond and improve or the slower group who are much tougher to coach and don't seem to improve? The top group will reach a decent level without my help, the slow group will probably stop running. Tough call.