There exists a point at which an instrument becomes truly challenging. Once the basics are out of the way, the music reading is all firmly in place, and students get their first taste of true intermediate repertoire it can be a make-or-break moment. Many students at this point will start to look at other instruments. Whenever I have students who are going to quit in order to take up another instrument I always warn their parents about this. Learning a new instrument is easy at first, but once it gets difficult the same thing is likely to happen. If you have a transfer student who took a year and half of more than one other instrument, watch out, you may lose her to flugelhorn next summer.
The "Go Easy" Parents
Some parents like a strict teacher, many do not. Maybe it's a generational thing, that current parents grew up in a border zone between knuckle slapping schoolmarms and laissez-faire households, but it seems like the stern, nagging piano teacher is a figure of the past. I've had a number of parents insist to me that they're looking for a teacher who wouldn't push their children too hard. Often the more you get into it, it looks like they're seeking a teacher who has exceedingly low expectations. This is a tricky situation, because although you may not be a particularly strict teacher, you also know that learning an instrument takes discipline. At some point you will want to be able to say "Yes, your child will have to practice. Because he will never learn anything if he doesn't." But you will probably just say "We'll see what we can do!" because in the end, you're a pushover.
The Miracle Teacher
Some parents are not looking for a teacher who will motivate and get their kid interested in piano, they are looking for a teacher who will transform their child into a perfect musician, with little to no work on the student's part. If your transfer student has had more teachers than years of lessons, there's a good chance that this is the underlying problem. There is a belief in our country that teachers are the beginning and end of education. A good teacher is important, but the student also has to have good habits. Parents need to emphasize to the child that hard work is the road to any acquisition of skill. A good teacher can work tirelessly to teach a brick wall how to play piano, but that wall will never progress to early-advanced repertoire. If your student has taken lessons from every other teacher in the school, talk to those teachers and find out why they transferred. Then watch for those same signs.
I've only received (and lost) a few students who are as well traveled as these. Some of them have even stuck around for quite awhile now. One thing that I offer is a pop-piano curriculum which is a nice break from the standard fare that most teachers will offer. Students who are transferring around a lot often enjoy playing piano, but get frustrated with the weekly grind of difficult classical pieces. I emphasize that learning a new style of playing is not going to be easy, and takes just as much discipline, but I think the very act of changing tracks can be refreshing enough to settle students down for a bit. We'll see though, the future is wide and there are still other teachers out there.