I try to be kind and patient. BUT... New students should join the existing class and do their best to fit in. Personally, I grow weary of spending time paired up to a hack newbie who's never coming back, while my Shodan test draws ever closer.
Doesn't really cast me in a golden light, I know. That's why I do all that meditation- it keeps me from acting like this all the time. Well, I'll get my instructor's certificate next year. I can be generous then.
Bill, the thing is, I find I learn nearly as much assisting beginners with their training as I do practicing with fellow established students. As I noted, the beginners will progress far quicker with good ukes than they will with other beginners. If you want good partners, you have to actively train them. And I always remember that Omori Sensei (8th dan iai/7th dan kendo) always took the beginners to teach. He focused on bringing the lowest in the dojo along the fastest. He would train everyone, but he took special care to focus on the new students. The result was they learned quickly and didn't stay new students for long.
The care and attention might also contribute to a higher retention rate.