When the nage applies an Aikido technique, the uke takes a fall. This act of the uke is known as ukemi.
As a beginner I am quiet awkward at taking an ukemi. As a nage also I tend to think about the move and at times it gets confusing. The teacher does not pair two beginners because both of them might not do the technique correctly. Moreover, the beginner Aikidoka can learn from the experienced partner.
Some of the senior Aikidokas are quiet helpful and show me the moves if I don't get it. I would have expected this from all Aikidokas but that is not the case. There is one guy who avoids pairing up with a beginner. If you approach him he will pretend that he did not see you and go to some one else. Once he did not have any choice but to pair with me. While practicing he had an eye on the others. At the first available opportunity he ran off to some one else even though the teacher had not asked us to change partners. I was a bit amused at his selfishness.
There are a couple of Aikidokas who don't show much regard to the beginner and tend to rough you up. Couple of times my arm muscles hurt because of this. Another beginner who had started practice around the same time as me had the same complaint. He was wondering if it would be useful to point this out to the techer. I told him it was not a good idea. Once we start getting the basics right then it should not matter if our partner is rough.