Basically my thoughts as well.I actually don't care at all about the whole age thing, it's either legal or not but going to a school to do a talk as part of your job, and then actually sleeping with them is a bit fucked up. That's about as unprofessional and unethical as it gets. You're there as part of your job not to get your dick wet.
If they met socially outside of work fair enough it shouldn't be news but that's really unprofessional.
If he received nudes from a 16 year old, he's crossed into child porn territory and could be in serious trouble, and not just with the NRL.