I have never asked a dancer not to return to a dance.
As a caller, organizer, and as a dancer, I have often suggested other dance locations that might be more suitable for their skill level. For instance, I often refer dancers with difficulties to a the local community dance that I organize, and sometimes call, or to smaller, beginner friendly dance communities.
I have recently begun teaching six week Adult Ed sessions, that I call an "Introduction to Traditional Country Dance". Often these dancers/students have dancers that would have trouble elsewhere. With many, the issue is that English is a second language, others have physical or other challenges.
I also lead a seniors' community dance session weekly, and the dancers range from 60-85 years old. Most do well at community level dancing, and several have danced at the local contra communities.
Both of the above situations afford newer dancers opportunities to learn basics like Heys, Ladies Chain, Square Thrus, and Swings. in a less intimidating environment. They also allow for much more repitition/drilling than at a typical contra dance evening.
I also suggest to these dancers that they attend the pre-dance workshops even if they do not feel that they are necessary. These workshops help newer dancers adjust to the voice and style of the evening's caller, and provide a quick review of many basics.
Despite all this, I have dancers that still freeze when they encounter a R&L Thru in a dance, especially if there is a Ladies Chain, or a Square Thru in the same dance.