EXPERT advice was dismissed by the education minister in allowing commercial exams boards to offer GCSEs that have experiments that do not count towards grades.
Schools can buy new science GCSEs from English boards, which are assessed solely through a written exam.
The decision by Peter Weir to maintain an `open market' is at odds with the views of scientific experts.
It also reverses a decision made by the DUP minister last summer.
Then, Mr Weir said new science courses from English awarding organisations should not be offered because there would be no marks for practical assessments.
Science exams from the north's Council for the Curriculum, Examinations and Assessment (CCEA) still include assessment of practicals that count towards overall grades.
A letter sent to schools this month reveals Mr Weir has changed his mind.
From this year, schools can use CCEA courses or those offered by English-based boards.
It has emerged that both CCEA and a range of science experts advised against allowing English boards to offer new GCSEs in the north.
The Royal Society of Chemistry, Institute of Physics, Royal Society, Royal Society of Biology and The Association for Science Education all said "direct assessment should remain a component of assessment of practical work".
In opposing changes in England, they said practicals should be "specified broadly enough to avoid a narrowing of student experiences and highly predictable examining, and to allow teachers to plan how best to engage their own students".
In England, Ofqual pushed ahead with its plan to stop science practical work contributing to grades in the face of opposition from the British government.
Then education secretary Nicky Morgan said the change that confined assessment to written exam questions "was in danger of holding back the next generation of scientists".
The matter was discussed at CCEA council in December last year, and advice issued to the Department of Education.
"The arguments for retaining practical assessment are supported by the relevant learned bodies and societies," CCEA concluded.
"Views from expert representative bodies are that the learner's interests are best served by a broad practical experience and assessment of practical skills will encourage schools to continue to develop practical skills."
The Department of Education said in forming its advice, CCEA made available a questionnaire to a wide range of groups.
The majority of respondents were schools, a spokeswoman said, with more than two-thirds indicating support for allowing assessment of practical skills through written exams. The Education and Training Inspectorate agreed with this view, she said.
GCSE science offered in England, she added, were required to have 15 per cent of available marks relating to questions on practical work. With CCEA GCSEs, 25 per cent of available marks relate to practical work. Of, 17.5 per cent is for an exam with questions based on practicals candidates are expected to have completed throughout their course. The remaining 7.5 per cent is for a practical activity that pupils will carry out under controlled assessment conditions.
"The minister took into account all of the advice and evidence presented to him before arriving at his decision and he is content that maintaining as wide a choice as possible for schools is important and his decision was taken in the interests of pupils," she added.