Tony Conroy, head of St Ninian's High, Kirkintilloch, found that his prediction was as wrong as HMI's and that results were markedly better than the benchmark he had set.
Fifty per cent of the year group in the 700-pupil Roman Catholic secondary gained five Standard grades at the top two levels, a staggering 66 per improvement on a figure of 30 per cent two years ago.
HMI's target was 40 per cent, up 10 per cent from the baseline. Mr Conroy thought that unrealistic and negotiated the figure down to 34 per cent, a move he says was welcomed by staff.
St Ninian's was well below the East Dunbartonshire average two years ago and is now well above for Standard grades 1-2. The improvement at national level is only expected to be 5.3 per cent over the next two years.
At Higher level, the percentage gaining five passes at grades A-C has risen to 15 per cent, from 8per cent two years ago and well above HMI's target of 9 per cent. The school hit the accepted target of 24 per cent gaining three Highers at grades A-C.
Mr Conroy backs the principles of target-setting - which is being enshrined in the first piece of education legislation in the new Scottish Parliament - but refuses to accept the Audit Unit formula.
St Ninian's outstanding results highlight the unrealistic basis of target-setting, he maintains. "I've no great confidence in free meal entitlement as a means of benchmarking schools and in the HMI approach to target-setting. I do accept we have to be compared but it should be like with like."
He added: "If they could benchmark more accurately, I would be happier. A lot of pupils do not take up free meals because of the stigma but footwear and clothing grants carry no stigma because they are anonymous."
Mr Conroy still feels he was correct in renegotiating targets downwards. "I did not believe they were realistic. I think it was a motivational factor for the staff at the time I negotiated targets with the local authority. The fact that I negotiated targets downwards did not limit our ambitions. We have not failed to stretch ourselves."
Mr Conroy did not dispute the Higher targets as they were based on previous Standard grade performance. "The results this year have been so exceptional there has been added value."
St Ninian's has been named as a new community school pilot, was runner-up last year in the Scottish Ethos Network awards and had its prizes presented by Sam Galbraith, the Children and Education Minister and local MSP. Sharing good practice is the best way of improving, the head insists.
Mr Conroy, who took over three years ago, said: "You can always improve but not all improvement comes from teaching and learning. A lot comes from motivating the youngsters and one of the reasons they do not do well is because they are not aiming high enough.
"High expectations are now the norm and you have got to focus on youngsters as individuals. They did not believe how able and talented they were. This improvement suggests a massive improvement by a lot of them."
He added: "We surpassed our own expectations and maybe the message is that we cannot have too high expectations."
St Ninian's has also virtually eliminated the performance gap between boys and girls. There is now only a small percentage difference between the two with girls doing marginally better.