Okay I had a student that cannot produce a sound on the Yamaha student model clarinet yet she can get one out of my professional wooden clarinet.

I have a Vito plastic clarinet which I am going to bring in for her to try but I was wondering if anyone knows what the difference is?

I now know it`s her instrument that is the problem not her but it seems she just can`t play the Yamaha`s....they have to much resistance for her.

The wooden ones are usually more resistant.
I`ve played a student Yamaha, and it is very free-blowing, so I`d say that there is probably some problem with the instrument- something not sealing properly or a similar problem.