After 3 years of teaching I'm finally properly teaching somone 3rd position! Thing is, as it's at least 20 years since I was myself taught it there are things I'm a bit unsure of. When my pupil shifts she slides the finger from 1st to 3rd position and back again. Is it OK to do this to start with? Or should I be encouraging her to make the shifts without sliding?

Sliding is good, as long as it's generated by a free fluid motion rather than a death grip! Double-stopping against an open string and listening for the arrival on the octave and down onto the sixth can be very helpful.

I tend to then talk about "taying on the note for as long as possible before shifting, like you don't want to leave it" to help speed it up correctly. Midnight Song in Fiddle Time Sprinters is invaluable with this.

That's very helpful, thanks!