JSO vs Big Science Competition vs ICAS Science: Which Should Your Child Sit?

Australian parents of science-keen kids face three big options each year, and the names alone don't tell you much. Here is how they actually compare — verified against the organisers' own websites — and a sensible sequence by year level.

The comparison at a glance

Sources for every row are listed at the end of this article.

What each competition is really for

ICAS Science: the benchmark

ICAS is run by Janison and, according to ICAS Assessments, covers Years 2 to 12 — the only one of the three open to primary students. Its grading is cohort-based and consistent every year: High Distinction for the top 1%, Distinction for the next 10%, Credit for the next 25%, Merit for the next 10%, with medals for the top scorer in a region. That makes it the best benchmarking tool of the three: you learn precisely where your child sits against the national cohort. In 2026, the Science sitting window is 17–21 August, with school Parent Payment System registrations closing 20 July and final entries closing 27 July, according to the ICAS event calendar. School entry costs AU$21.95 per subject; independent entry through an ICAS testing centre costs more (AU$57.75).

Big Science Competition: the confidence builder

The BSC is run by Australian Science Innovations — the same organisation behind the JSO and Australia's olympiad teams. According to ASI, it is a 50-minute, mixed-format online competition for Years 7–10, with four paper levels aligned to the Australian Curriculum, testing science knowledge, critical thinking and problem solving. At $9.35 per student it is the cheapest of the three by far. The 2026 window ran 4–15 May. Students receive a certificate indicating performance, and schools receive reporting against class, school and national averages. Think of it as the friendly on-ramp: real competition experience without olympiad-level difficulty.

Junior Science Olympiad: the pathway exam

The JSO, also run by ASI, is the serious one: a two-hour online exam across all four sciences for Years 7–10, held in 2026 on 10 and 12 June at $22 per student. It is the only competition of the three connected to a national talent pathway — top performers are invited to the JSO Spring School, from which six students are selected for Australia's International Junior Science Olympiad team, and the same skills feed directly into ASI's senior Australian Science Olympiad Exams, Summer School and international teams. Free past papers (2020–2025, with answers) are on the ASI website — see our 8-week JSO preparation plan for how to use them.

A sensible sequence by year level

• Years 2–6: ICAS Science is the only option of the three. Sit it annually if your child enjoys it — the year-on-year reports show growth clearly.
• Year 7: Start with the Big Science Competition (May) as a low-pressure introduction, then ICAS Science (August). Keen students can attempt the JSO too — the Years 7–8 paper is pitched for them.
• Year 8: BSC and ICAS again, and add the JSO with proper preparation. A Year 8 result gives useful feedback before the stakes rise.
• Years 9–10: The JSO becomes the priority — this is the window for Spring School and IJSO selection (ASI requires Spring School students to be under 16 as at 31 December and hold Australian citizenship). Keep ICAS Science as the benchmark; keep the BSC if the calendar allows.
• Years 10–12: Graduate to ASI's senior Australian Science Olympiad Exams (held 27–30 July in 2026, $22 per exam), the gateway to Summer School and Australia's international olympiad teams.

The three are complementary, not competing: the BSC builds confidence, ICAS benchmarks progress, and the JSO opens doors. A motivated Years 7–10 student can comfortably sit all three for under $60 a year in entry fees at school rates.

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