OSN Guide: Picking a Field, Covering the Syllabus, Practising Problems

OSN stands for Olimpiade Sains Nasional, the National Science Olympiad, organised under Indonesia's education ministry by its national achievement centre (Puspresnas) and talent development agency (BPTI). Students climb it in four steps. First comes an internal selection at school, which decides who represents the school in each field. Next is the district or city round, known as OSN-K, followed by the provincial round, OSN-P, and finally the national round, where gold, silver and bronze medals are awarded.

Each step raises the kind of question asked. School selection papers usually sit close to classroom material. OSN-K starts to demand reasoning that rarely shows up in a regular class test. OSN-P leans on problems that need several linked steps of thought, and the national round probes a depth that edges towards international olympiad problems. A student who drills OSN-K archives first, then shifts to OSN-P archives once district-level questions feel comfortable, is matching their practice to this ladder.

A simulation, a practice round on the exam platform, usually comes before each round. It is a technical rehearsal of the online exam platform, where students get used to the question layout, moving between items and submitting answers. Nobody is eliminated by it. Students use it to make sure their device and connection work, so that on the actual day their whole attention goes to the problems.

National medallists may go on to selection for international olympiad teams, such as the IMO in Mathematics, IPhO in Physics, IChO in Chemistry and IOI in Informatics. For everyday practice, the ladder is most useful as a sequence of targets: master the question style of the round directly ahead.

Puspresnas and BPTI publish an OSN syllabus for every field, listing competencies from the basics up to olympiad level. For a student, this document marks the borders of the study territory. Topics inside it deserve the effort, and topics outside it can wait. Without that map, OSN study easily drifts into fascinating chapters that are rarely tested, and preparation time goes to material that never appears in selection.

Using it is simple, though it takes care. The student copies the syllabus topics into one table and gives each a single mark: able to explain it back, studied but still shaky, or never touched. The table immediately shows the work ahead. Shaky topics are usually the quickest to fix, while untouched ones need scheduling with a textbook from the grade above or an olympiad book for that field.

The same table stays in use once problem practice begins. Each past-paper question gets logged against its topic, which reveals topics that have been drilled often and those that have never come up. Close to selection, the student scans the table to confirm that no syllabus topic is completely empty, and any stragglers get dedicated practice in the final weeks.

Syllabi for primary, junior high and senior high differ in scope, and content can be revised from year to year. Students download the latest version from the official site at the start of each preparation season and compare it with last year's table to spot additions.

Each senior high field has large content blocks that keep recurring. Olympiad mathematics rests on four branches: algebra (equations, inequalities, functions), geometry (plane and solid figures, transformations), combinatorics (permutations, combinations, probability) and number theory (factorisation, modular arithmetic). Number theory and combinatorics rarely get deep treatment in class, so students usually build them from olympiad books.

Physics spans mechanics, thermodynamics, electricity and magnetism, and optics and waves including interference and diffraction. Chemistry divides into physical chemistry (thermochemistry, kinetics, equilibrium), organic chemistry (structure, reactions, synthesis), inorganic chemistry (transition elements, coordination compounds), and qualitative and quantitative analysis. Biology covers cell biology, genetics, ecology, and anatomy and physiology, with many questions presenting experimental data to interpret.

Informatics starts from basic algorithms such as sorting, searching and greedy methods, then moves on to data structures and dynamic programming. OSN-K tests them through multiple-choice, short-answer and true-false questions, and from OSN-P onwards programming tasks are added that must be correct and fast enough. Astronomy includes positional astronomy (celestial coordinates, sidereal time), astrophysics (stars, galaxies, spectroscopy) and cosmology. Economics covers micro, macro and data analysis. Earth Science covers geology, meteorology and oceanography, and Geography covers physical geography, human geography and cartography.

A list like this lets a student break the field into study blocks. One block is studied until the student can handle OSN-K questions on it, then the next block opens. Every few weeks the student returns to earlier blocks with mixed problems, so the first material does not fade as new material arrives.

The practice material closest to the real thing is past OSN-K, OSN-P and national papers. Five to ten years of archives give a fair picture of patterns, frequently tested topics and the difficulty of each round. Archives with worked solutions are more useful, since the solving methods can be studied, especially for problems the student could not crack.

The order of working through them affects how much they teach. Students start with the oldest OSN-K papers, tackle them topic by topic without a time limit, and give each problem around twenty to thirty minutes of real struggle before opening the solution. That struggle matters, because a solution sticks far better once the student has felt exactly where they got stuck. The most recent OSN-K papers are kept untouched for timed simulations in the months before selection.

Reading a worked solution also has a method. The student reads up to the first step they had not thought of, covers the rest, and tries to continue alone. If stuck again, they reveal one more step. This staged reading leaves part of the work for the student, so the key idea of the problem is understood from the inside. Afterwards they write one sentence about that key idea beside the problem.

Archives need checking too. Copies circulating in online repositories sometimes carry typos or wrong answer keys, so students favour sources with complete worked solutions and confirm doubtful answers with a coach.

Practising chapter by chapter tells a student the method in advance, since every problem on the page comes from the same chapter. In a selection round that clue disappears. A number theory question can be followed by a geometry one, and the student has to recognise the problem type before choosing an approach. Interleaved practice trains that recognition by mixing problems from several subtopics in one session.

Mixed practice feels harder, and early scores tend to look lower than in chapter-by-chapter work. That is normal. Students can begin by mixing two topics they already handle well, then add topics one at a time. A mixed session should always include a few problems from older blocks, so it doubles as revision.

Full timed papers at official length come in once most syllabus topics have been practised at least once. The student sits a complete paper in conditions close to the real round: one seat, a strict clock, no notes. The working order being trained is to secure the familiar questions first, flag the stubborn ones, and return at the end, so time does not drain away on a single item. Results are then dissected in the error log with the same care as ordinary practice.

Near selection, physical condition counts as part of preparation. Eight to ten hours of sleep, the amount recommended for teenagers, regular meals and light exercise protect concentration. Students also rehearse a way to settle themselves when a hard problem appears mid-paper, such as taking a breath, rereading the conditions, then moving on to another question, so the habit is automatic by the day of the round.