SOF IMO vs ISO vs IEO: which exam to choose, and why NSO disappeared
By The Sophoz Curriculum Team
The short answer. SOF's National Science Olympiad is now the International Science Olympiad (ISO), and the National Cyber Olympiad is now the International Computer Science Olympiad (ICSO). The three exams worth comparing are IMO, ISO and IEO, because they are the only three with a second level. They cost the same ₹170, run for the same hour, and carry the same 25 % Achievers weighting. What separates them is how much of the paper is reasoning rather than subject knowledge: 25 % in IMO, 16.7 % in ISO for classes 5 to 10, and none in IEO.
First: NSO no longer exists, and most guides have not noticed
The computer olympiad rename is stated outright by SOF's own official preparation platform: "NCO has been renamed ICSO" (sofolympiadtrainer.com), on a page that still defines NCO as "a cyber concepts and knowledge competition for students of class 1 to class 12".
The science olympiad rename is evidenced rather than announced. SOF's exam page now presents the exam throughout as the "International Science Olympiad (SOF ISO)", for classes 1 to 12, one hour, ₹170 (sofworld.org/iso), and SOF's legacy /nso/ URLs now serve ISO content. We could not find a dated SOF announcement of the science rename, and we are not quoting one.
What changed: the names. What did not change: the syllabus, the pattern, the fee, the levels, the awards. A child preparing for what a workbook calls NSO is preparing for ISO. Nothing needs redoing.
Where the old names are still in circulation, as of 21 September 2026:
| Source | Still uses | Notes |
|---|---|---|
| SOF Olympiad Trainer, Google Play listing | NSO, NCO | The official preparation platform |
| MTG product URLs | nso | The publisher of the official workbooks |
| SOF's own legacy URLs | /nso/ | At least one live page still titled "SOF NSO FAQs" while serving ISO content |
| Oswaal, Vedantu, Careers360 olympiad pages | NSO | Also publishing a fee figure of ₹125 to ₹150 against SOF's official ₹170 |
We could not locate a dated SOF announcement of either rename, so the year it took effect should be treated as unconfirmed. The fact of it should not: SOF states it in its own words on its own page.
One more naming caution. As of 2026-27, "ISO" also refers to Indian Talent Olympiad's International Science Olympiad and, as "iOS", to SilverZone's International Olympiad of Science. Three bodies, similar acronyms, unrelated exams. When a school circular names an exam by acronym, ask which foundation is running it.
What the three exams share
All figures from sofworld.org/pattern-questions-and-marking-scheme.
- ₹170 per student per exam, inclusive of GST, plus up to ₹30 the school may add
- One hour, multiple choice, sat in school
- 35 questions for 40 marks in classes 1 to 4; 50 questions for 60 marks from class 5
- Achievers Section: five questions carrying 25 % of total marks, in all three
- Two levels, for classes 3 to 12 only. Classes 1 and 2 have no Level 2 route
- Same Level 2 criteria: top 5 % class-wise, or zonal top 25, or class topper at a school with at least 10 candidates in that class scoring at least 50 %
- Registration through the school only. Results in eight weeks
So the choice is not about cost, format, difficulty of qualification or effort. It is about what the paper contains.
Where they differ: the section breakdown
Classes 5 to 10, the band where most families are choosing
| Section | SOF IMO | SOF ISO | SOF IEO |
|---|---|---|---|
| Logical Reasoning | 15×1 = 15 marks (25 %) | 10×1 = 10 marks (16.7 %) | None |
| Core subject | Mathematical Reasoning 20×1 | Science 35×1 | Word and Structure Knowledge 30×1 |
| Applied section | Everyday Mathematics 10×1 | None | Reading 10×1, Spoken and Written Expression 5×1 |
| Achievers | 5×3 = 15 marks (25 %) | 5×3 = 15 marks (25 %) | 5×3 = 15 marks (25 %) |
| Total | 50 Q / 60 M | 50 Q / 60 M | 50 Q / 60 M |
Classes 1 to 4
| Section | SOF IMO | SOF ISO | SOF IEO |
|---|---|---|---|
| Logical Reasoning | 10×1 (25 %) | 5×1 (12.5 %) | None |
| Core subject | Mathematical Reasoning 10×1 | Science 25×1 | Word and Structure Knowledge 15×1 |
| Applied section | Everyday Mathematics 10×1 | None | Reading 10×1, Spoken and Written Expression 5×1 |
| Achievers | 5×2 (25 %) | 5×2 (25 %) | 5×2 (25 %) |
| Total | 35 Q / 40 M | 35 Q / 40 M | 35 Q / 40 M |
The single most useful fact in these tables: SOF IMO is a quarter reasoning and a quarter Achievers, meaning half the paper is not straightforward year-level mathematics. That is why children who are strong in school maths sometimes score unremarkably, and why the exam is worth sitting even when school maths is already comfortable.
SOF IEO has no reasoning section at all. It is the most purely subject-based of the three, which makes it the most predictable to prepare for and the least likely to surprise a well-prepared child in either direction.
The Level 2 change nobody flags
At Level 2, across all three exams, the Logical Reasoning section disappears entirely and its marks are absorbed into the subject section.
| Exam | Level 2, classes 5 to 10 |
|---|---|
| IMO | Mathematics 45×1 + Achievers 5×3 |
| ISO | Science 45×1 + Achievers 5×3 |
| IEO | Word and Structure Knowledge 35×1, Reading 10×1, Achievers 5×3 |
For IMO this is a structural change, not a detail. A child who qualified partly on reasoning strength now faces a paper that is 75 % mathematics and 25 % Achievers, with the section they were good at removed. Level 2 is a harder paper in a different shape, and almost no preparation material says so.
Which one for which child
Choose SOF IMO if the child enjoys puzzles, patterns and problems with no obvious starting point. Half the paper rewards that directly. It is also the right choice if the goal is broad thinking practice rather than a subject result, because reasoning and Achievers together outweigh the year-level mathematics.
Choose SOF ISO if the child is curious about how things work rather than about numbers specifically, and can read carefully. Science at 35 of 50 questions is the highest subject concentration of the three at classes 5 to 10, so preparation maps to a syllabus more directly.
Choose SOF IEO if the child reads widely and the goal is to consolidate that into structure: vocabulary, grammar, comprehension. It is the most learnable of the three and the least dependent on a knack, which makes it the best first olympiad for a child who has never sat one.
Choose more than one only if the child wants to. Three subjects is ₹510 to ₹600 and three separate preparation tracks across October to December, which is where the structured-practice benefit starts turning into exam fatigue.
A reasonable default for a first year: one exam, chosen by what the child actually likes, sat with light preparation, treated as information. Add a second next year if the first was enjoyed.
The other five SOF exams, briefly
SOF ICSO (computer science, classes 1-10) added a section named "AI, Robotics and Information Technology" from class 3 upwards, which is a recent syllabus change worth knowing about. Single level.
SOF IGKO (general knowledge, classes 1-10) splits General Awareness, Current Affairs and Life Skills. Single level, and the most dependent on general reading rather than preparation.
SOF IHO (Hindi, classes 3-10) runs शब्द और व्याकरण बोध and रचनात्मक बोध, with the Achievers Section as मेधावी खंड. Single level. Almost no third-party preparation material exists for it, which cuts both ways.
SOF ISSO (social studies, classes 3-10) runs undifferentiated Social Studies for classes 3 to 8, then splits into History, Geography, Political Science and Economics for classes 9 and 10. Single level.
SOF ICO (commerce, classes 11-12) covers Economics, Business Studies and Accountancy. Single level.
None of these five has a Level 2, which is the practical difference: they are one exam, one date, one result.
Dates for 2026-27
| Exam | Date 1 | Date 2 | Date 3 |
|---|---|---|---|
| SOF IEO | Wed 30 Sep 2026 | Tue 27 Oct 2026 | Tue 17 Nov 2026 |
| SOF IMO | Fri 23 Oct 2026 | Thu 26 Nov 2026 | Thu 10 Dec 2026 |
| SOF ISO | Fri 30 Oct 2026 | Thu 19 Nov 2026 | Thu 3 Dec 2026 |
Schools pick one date per exam. Level 2 dates are unannounced; SOF states they will be published by December 2026, tentatively the second or third Sunday of February 2027.
Full detail on all eight exams, awards and cutoffs is in our SOF 2026-27 guide.
Frequently asked questions
What is the difference between IMO and NSO? NSO no longer exists under that name: SOF's science olympiad is now ISO, the International Science Olympiad. Comparing SOF IMO with SOF ISO, both cost ₹170 and run for an hour with the same Achievers weighting, but IMO devotes 25 % of marks to logical reasoning against 16.7 % for ISO at classes 5 to 10, and ISO concentrates 35 of 50 questions on science.
Is NSO the same as ISO? In practice, yes. SOF now presents the exam as the International Science Olympiad (SOF ISO) throughout its own exam page, and its legacy /nso/ URLs serve ISO content. SOF has not published a dated announcement of the change, unlike the computer olympiad, where its official platform states plainly that NCO has been renamed ICSO. The syllabus, pattern, fee and levels are unchanged. A great deal of published material, including SOF's own Play Store listing, still uses the old name.
What happened to NCO? It is now ICSO, the International Computer Science Olympiad, and it has carried a section on AI, Robotics and Information Technology from class 3 upwards. It is a single-level exam.
Which SOF olympiad is easiest? No SOF exam is easier by design; all three two-level exams share the same pattern, weighting and qualifying criteria. IEO is the most predictable to prepare for because it has no logical reasoning section and its content maps to a syllabus, which makes it the most common first choice.
Which SOF exams have a Level 2? Only IMO, ISO and IEO, and only for classes 3 to 12. ICSO, IGKO, IHO, ISSO and ICO are single-level exams, and students in classes 1 and 2 have no Level 2 route in any subject.
Should my child take all three of IMO, ISO and IEO? Three subjects costs ₹510 to ₹600 and means three preparation tracks running between October and December. For a first year, one exam chosen by what the child enjoys, prepared for properly, produces more of the benefit than three prepared for thinly.
Verified 21 September 2026 against sofworld.org. The year of the NSO to ISO and NCO to ICSO renames is unconfirmed; the renames themselves are stated by SOF.