Any teacher who says they don't have a good idea which kids are going to be hard work just by reading the register is fibbing. I'm yet to meet a well behaved Kayden, Hayden, Jayden, Alfie or Archie and I'm yet to meet a well behaved Jaxon.
And just like everyone knows how old Tracey is before meeting her, everyone will also know how old Jaxon is.