SOF International Science Olympiad (ISO, formerly NSO)

Class 1 to 12 (Level 2: Class 3 to 12) · run by Science Olympiad Foundation (SOF) ↗

SOF's science olympiad, held in schools. SOF now calls it the International Science Olympiad (ISO); it was the National Science Olympiad (NSO), and SOF's web addresses still use /nso/.

The facts, from the official site

Level 1 dates 2026-27: 30 October 2026, 19 November 2026 and 3 December 2026 (the school picks one). Source: sofworld.org ↗
Pattern: 60 minutes. 35 questions for Classes 1-4, 50 for Classes 5-12, multiple choice, in English. Classes 1-10: Logical Reasoning, Science and an Achievers Section; Classes 11-12: Physics and Chemistry, an Achievers Section, and Mathematics or Biology. Source: sofworld.org ↗
Fee and registration: ₹170 (GST included) per student per olympiad for schools in India; a school may add up to ₹30. Students register through their school, which acts as the exam centre. Source: sofworld.org ↗

Syllabus

SOF publishes a syllabus for each class. Official syllabus: sofworld.org ↗

Free official papers and pages

SOF ISO syllabus, class by class ↗SOF's own syllabus page; pick your class (sofworld.org)
SOF ISO free sample papers 2026-27 ↗SOF's own free PDF sample paper for each class, no login (sofworld.org)
SOF ISO exam dates ↗The Level 1 dates SOF has announced for 2026-27 (sofworld.org)

How to use these papers

Read the syllabus for your class first, then try one official paper under the real time limit, without help.
Mark it with the official answer key, and list each question you got wrong by topic. That list is what to study next.
Try the next paper a week or two later and compare which topics are still on your list.
Your school registers you and tells you which of SOF's dates it has chosen.

Good to know

Level 2 is open to Classes 3-12. SOF says it invites the top 5% of each class (internationally) from Level 1, the top 25 of each class in each zone, and each school's class topper who scores at least 50% where at least 10 students of that class sat the paper. SOF had not published the Level 2 dates on 23 Oct 2026; it says schools are told once they are fixed.
On SOF's sample-papers page (23 Oct 2026) the "Class 11" link opens the Class 10 paper; use the Class 12 page or ask your school for the Class 11 paper.
SOF's sample-paper pages also advertise a publisher's paid practice books. Shishya does not copy or link those books; the sample papers linked here are SOF's own free PDFs.

Dates and updates for this exam on Shishya: SOF ISO (NSO) exam page.

Read on the official sites on 23 Oct 2026. Dates can change; the conducting body's site is the final word.