They show up with an instrument that is difficult to play. Of course they don't know why: perhaps they assume it is supposed to be difficult! When I tell them to take it to a repairman or luthier and have the setup adjusted, they are surprised. Maybe this sounds dire, as if I'd told them it is broken and needs to be repaired, and so they often chafe. 

But usually I can persuade them and oh, the difference it makes! With low action at both the first position and up higher on the neck, playing becomes not only possible but pleasurable. 

It is critical to know and work closely with a local person who can do this for the instruments you come into contact with. I've several times invited my good friend, luthier Jim Gangi, to come into the school and set up a portable workshop. He brings sufficient tools to make minor adjustments and assesses everyone's guitars for possible additional adjustments or repairs. Many would get their action lowered on that day. This is a great service to offer if at all possible. It is normally great for the luthier as well, as he can generate business and spend time one-on-one with all the serious students. 

We understand intuitively that our cars need regular maintenance. So do our guitars! One time a visiting guest artist, staying at my home, was playing my guitar and remarked "hey this is unfair, it is so easy to play!!" Yes, and his should be too!

Have your action adjusted if it needs it. Your hands will thank you and your music will suddenly be so much easier to play.