More than three-quarters of Scotland's P7 and S2 pupils failed to gain even half marks at the target levels for their stages, according to the latest attainment survey.
The Assessment of Achievement Programme, in its sixth survey of science, also found that fewer than 10 per cent of upper primary and lower secondary pupils were "secure" (attaining 65 per cent or more) at the target levels - level D for P7 and level E for S2.
Just over a third of the P7 pupils were rated secure at level C and just under a fifth of the S2 pupils were similarly classified at level D - the levels below their targets.
No S2 pupils were secure at Level F and virtually no P7 pupils were secure at Level E.
The report found: "On the basis of a very modest set of common tasks, that is, tasks from the 1999 survey that were reused here, there is no evidence of any change in pupil attainment since 1999."
The picture was more optimistic at the P3 and P5 stages, however.
Three-quarters of P3 were classified as being secure at Level A and more than half were also secure at Level B. Similarly, three-quarters of the P5 pupils were secure at Level B and around a quarter were secure also at Level C.
The survey was carried out in May and June 2003, involving almost 10,000 pupils in almost 600 schools.
A spokesperson for the Executive pointed out it had taken place just after changes had been made to the 5-14 guidelines for environmental studies and that some schools may not have had time to incorporate the changes into their teaching.
The survey of pupils' investigative skills found that a quarter to a third of the pupils had to be given assistance by the field officers before they could show enough evidence of relevant skills for them to be judged at one level or another for each of the attainment targets included in the checklists.
The report added: "On a similar basis, 10-25 per cent of the pupils could not be judged at a level at all because they did not show evidence of the behaviour concerned, with or without prompting from the field officer."
Meanwhile, the first AAP survey of social subjects mirrored the science survey in that results for P3 and P5 were good overall, but were less so for P7 and S2.
Tests focusing on enquiry skills found three-quarters of P3 pupils were secure (65 per cent marks plus) at Level A and just under half were also secure at Level B (the level expected for P4). Over three-quarters of P5 pupils were secure at Level B and just under 40 per cent were also secure at Level C (the level expected for P6).
At the "problem" stages, over 70 per cent of P7 and over 60 per cent of S2 demonstrated at least basic skills at their expected levels D and E, scoring more than half of the available marks. However, by the more stringent standard of "secure", fewer than half of P7 and under 40 per cent of S2 pupils were reported to be at those levels.