Ignoring the money
Once, I applied for a job that said a higher salary could be made available "for a suitable candidate". I was experienced, with a good track record, and said I was only interested if I could have the money. They respected that and I got the job.
Now schools have more leeway, and if you feel you have a genuine reason - qualifications, experience - for querying the money on offer then it would be a mistake to let the moment go. Schools are increasingly aware of the principle of paying for the people who will do the best job for their pupils.
What's the right thing to do?
When I investigated this for my Jobs and Interviews Pocketbook (Teachers' Pocketbooks, 2007), the consensus was that, given reasonable grounds, it was right to query the salary. I quoted a deputy head from the TES forums who reported saying, politely, at the "any questions?" stage of the interview that the salary "was a little on the low side". They gave him the job at an increased salary.