A student who has solved every past paper for their IB subject can still be surprised by their actual grade, because solving a question and meeting IB's specific assessment criteria for that question are not the same achievement. IB doesn't grade against a fixed points-per-step scheme the way some other boards do — it grades against published criteria like analysis, evaluation, and communication, and a technically correct answer can still fall short of the top band on one of them.

Why past papers alone don't reveal criterion gaps

Checking a past-paper answer against an official mark scheme confirms whether the content and method are broadly right, but it can't tell a student whether their specific phrasing, structure, or depth of reasoning would actually satisfy an examiner applying the criterion at the top band versus a middle one. That judgment requires someone trained in how IB examiners actually apply those criteria, reading the specific answer a student wrote.

What criterion-based marking actually catches

  • Whether a response demonstrates "analysis" versus merely "description" — a distinction IB grading takes seriously and generic self-checking usually can't judge.
  • Whether the command term in the question ("evaluate," "discuss," "to what extent") was actually answered to the depth that term requires, not just addressed superficially.
  • Whether a technically correct calculation or argument is communicated clearly enough to earn full marks under IB's specific communication criterion.

A common mistake: equating past-paper volume with genuine readiness

Solving a large volume of past papers builds familiarity with question styles and content, which is genuinely useful — but volume alone doesn't reveal whether a student's specific answers would satisfy an examiner's actual criterion-based judgment. A student can solve fifty past papers and still be making the same criterion-level mistake in every one, if nothing along the way is checking against the actual grading criteria rather than just the final answer.

What this looks like in practice

BuzzyBrains Academy's IB Test Series marks every mock paper against the same command terms and criterion-based grade descriptors real IB examiners use, with inline feedback on exactly which criterion a response fell short of and why — not just whether the final answer was broadly correct.

The IB Test Series page has the full pack details across HL and SL — worth a look if past-paper practice alone hasn't translated into the grade your child's understanding would suggest.