Technically there is also a minimum of six but occasionally we proceed with an undersized class anyway. That said, we find that the best evidence of learning is performance and, hopefully, your writing will improve as the result of the course. We do keep track of all our student's work and do provide transcripts when requested. We are pretty flexible on assignments. Our attitude is that it is your education and you will do what you need.
Most students stay on track.
A few fall behind and get caught up a bit later. People often take on more than they can handle or discover through the course that they are not as interested in writing as they had thought they were. It's a tough discipline. For various reasons, people don't complete a course. For example, we had one student who just lost her mother during a course and another who had to care for a sick aunt.