It is the first robust evidence to emerge on comparative pupil performance and may accelerate the demise of Standard grade as an S4 leaving exam.
Secondaries across Scotland are experimenting with the earlier introduction of Standard grade courses and the Dalziel findings bolster the view that the 5-14 curriculum has had its day in secondary schools. Extra space in the senior school would be devoted to making the Higher a two-year course over S4 and S5.
Brian Miller, Dalziel's headteacher, told secondary heads in East Kilbride on Tuesday that initial results were heartening. Parents are fully behind the earlier courses and in a survey eight out of 10 S2 pupils backed the move.
Announcing his findings at the Headteachers' Association of Scotland's spring conference, Mr Miller said that 10 days earlier his top groups in maths in S2 and S3 had sat the same exam under controlled conditions.
In maths reasoning, S2 pupils are doing just as well. "We have fired the second year up by saying, 'you will want to do as well as them', so maybe we should now be looking at third year and firing them up more," Mr Miller said.
"There is definitely increased motivation in S2. There is no doubt about that. There is definitely increased effort with homework and there are fewer referrals."
Mr Miller admitted that teachers had pushed the second years to compensate for their immaturity, giving them more exam practice and devising coping strategies.
In English, S3 pupils remain ahead in reading and writing by a grade point, as teachers expected. "They were close but second-year were behind. The gap was very narrow or none at all with the lower abilities. Is this surprising? At first you would say yes, but when you think about it but it is not. The poorer ones are still struggling a year on," he said.
Mr Miller said that the English department will gain an extra period next year in S3 and will use it to focus on writing. "In general terms, there is increased motivation, greater challenge for pupils who had already achieved a level E and across all levels, and better quality in the first draft essays. S2 pupils amazingly seem more focused than third-year pupils and again that's maybe our fault. They want to do just as well as the bigger ones."
Mr Miller said that the S1 course was now sharper and the dip in performance in S2 had been addressed. Moves to introduce other subjects earlier will wait until after next year's exams.
Mr Miller told The TES Scotland: "We are borrowing time from the later stages of 5-14, when a lot of kids start coasting, and giving it at Higher, when it is really needed. Higher is usually a two-term dash and nobody gets into university with good 5-14 grades."
Peter Peacock, Education Minister, says he supports any measure that prevents "the dip in attainment" in S1 and S2.