DD doesn't get as much homework as she expected (and she is pretty conscientious), she has produced some revision materials in her spare time. She is also exploring enrichment opportunities outside college - so we have a trip to Leeds already booked for December.
Peer marking can be very valuable - giving the marker a chance to see a different approach to the question, and both parties can develop their skills in seeing what the examiner is looking for. It is also a helpful skill for University where self organised study groups can really help with grades.
However this early in the year - and allowing the "marking" to happen outside of the classroom could be a real mistake. The teacher didn't know yet that there was a student who wouldn't take the process seriously (within a month or so they should be able to guess exactly which student had "randomly" got the essay when this kind of thing happens).
It is probably the students fault - but it could be that someone in that class is dealing with a really chaotic situation outside the classroom. I knew of one student who it was discovered that her alcoholic mother was deliberately deleting her homework on occasions - which is why she was handing in scrappy work, as she hastily tried to recreate it.