A lot of people who do the lantern test fail first time because they're told to report white, green and red lights but the white is incandescent (not a pure white) so it looks more orange often resulting in people making a call of 'red'.
Some doctors do this test infrequently and also don't know the deal.
Chase CASA to get a letter OK'ing a visit to the Victorian College of Optometry (yes..in Melbourne). The doctors there specialise in color vision and will run a bunch of tests before finishing up with the lantern test, by which time they will have a good idea of any color deficiency...
Best of luck to your student
