The system was first introduced in 2002.
Mr Walker said parents thought their child should be doing mathematics and English.
However, Mr Walker said many students these days didn't need a job which required just "pure Maths and English".
In their case, once they had satisfied the basic entrance level requirements for a course, they should opt to do a subject that is more beneficial to their chosen career path.
Secondary Principals' Association president Tom Parsons said increased teacher workloads under NCEA - identified as a continuing problem for education staff in the survey - was largely due to the system's higher pass rate aims.
Sixty-nine per cent of teachers said they supported NCEA in the survey, compared to 95 per cent of principals.
Mr Parsons said it was possible to have "100 per cent of your kids" pass under NCEA.
But this required an "inordinate" amount of work from teachers.
"A question can quite rightly be asked by parents and stakeholders - why isn't my student up to the required standard?" he said.
Latest figures show 86.1 per cent of Bay of Plenty Year 12 students who sat NCEA level 2 last year passed. This was up from 76.3 per cent in 2008.
Nationally, the NCEA level 2 pass rate was 83.6 per cent last year, compared to 75.7 per cent four years earlier.
Mr Parsons also said initial problems with the system had largely been teased out.
"As a rule of thumb it is a very, very good system... [which] requires very, very good, hardworking staff," Mr Parsons said.