IB ESS IA Criteria Explained: How It Is Marked

How the IB ESS IA criteria work

The IB ESS IA criteria for the course first assessed in 2026 divide the individual investigation into six criteria worth 30 marks. Criteria A-C are worth 4 marks each, while Criteria D-F are worth 6 marks each. The IA contributes 25% of the final ESS grade at SL and 20% at HL, although both levels complete the same investigation and use the same criteria.

Your teacher marks the report first. The IB then externally moderates a sample of work from your school to maintain a common international standard, so the school's marks may remain unchanged, rise, or fall.

Older resources may use criteria such as Identifying the Context, Planning, Applications, and Communication. These belong to the course assessed through 2025 and are not the correct main mark scheme for a current investigation.

The maximum report length is 3,000 words, and the IB recommends 10 hours for the investigation. Schools may organize that time differently. The official ESS subject brief confirms the assessment format, weighting, and word limit.

How marks are selected within a band

The rubric uses a best-fit approach. A marker compares the evidence across your work with the complete descriptor and selects the band that most accurately represents the criterion overall. Marks are not normally deducted through a universal one-mark-per-mistake checklist.

Some criteria contain bands such as 3-4 or 5-6. After identifying the correct band, the marker decides where the work belongs within it by considering its completeness and consistency. Command terms matter: describe requires detail, explain requires reasons or mechanisms, and evaluate requires a supported judgment about significance or effectiveness.

Length alone earns nothing. Every table, calculation, source, and paragraph should help satisfy a descriptor or answer the research question.

Criterion A: Research question and inquiry, 4 marks

Criterion A assesses whether you establish an environmental issue, support it with relevant research, and develop a focused question. Work in the 1-2 band may describe the issue incompletely or present a question with a weak connection to it. For 3-4 marks, the issue must be explained using sufficient background research, and the focused question must directly address it.

Background research should justify the variables, system, location, population, or range investigated. “How does pollution affect water?” is too broad. A stronger question is: How does distance downstream from a stormwater outlet affect nitrate concentration in River X during October 2026?

Avoid filling the introduction with general environmental history. Explain why the dependent variable is a meaningful indicator and build logically toward the precise question.

Criterion B: Strategy, 4 marks

Criterion B requires an existing or developing strategy connected to the environmental issue, followed by consideration of a tension between perspectives. The strategy could be a regulation, conservation programme, tax, technological intervention, management plan, campaign, or restoration project.

For 1-2 marks, a student may state a strategy and describe a resulting tension. For 3-4 marks, the strategy must be clearly described and the tension between economic, social, cultural, political, or environmental perspectives must be explained.

For an investigation into agricultural nitrate, relevant strategies might include fertilizer restrictions or vegetated buffer strips. Rather than stating that farmers and environmentalists disagree, explain how production costs, food supply, land ownership, enforcement, and ecosystem protection create competing priorities. The IB ESS curriculum update identifies this examination of perspectives as a feature of the current IA.

Criterion C: Method, 4 marks

Criterion C assesses whether the method is repeatable and can generate sufficient relevant data. Evidence may be primary or secondary, quantitative or qualitative, and may use experimental, fieldwork, database, survey, or other social-science methods.

A method in the 1-2 band is not repeatable or cannot produce sufficient data. For 3-4 marks, another informed person should be able to follow it without guessing essential details. Include relevant locations, equipment, timings, intervals, sampling rules, database filters, survey questions, controls, and ethical precautions.

There is no universal IB requirement for a particular sample size, number of repeats, or statistical test. Sufficiency depends on variability, the question, and the planned analysis. A materials list cannot replace a procedure, and group-supported work must still make your individual contribution clear. Use the RevisionDojo Criterion C guidance to check repeatability.

Criterion D: Treatment of data, 6 marks

Criterion D examines how clearly you communicate raw and processed data and whether the processing addresses the question. The 1-2 band reflects unclear communication, major errors, or processing that does not answer the question. The 3-4 band generally has clear communication but incomplete processing or minor errors. For 5-6 marks, raw and processed evidence must be clear and detailed, with correct processing that fully addresses the question.

Tables need informative titles, variables, units, and consistent precision. Graphs should have a defined analytical purpose. Qualitative evidence can be treated systematically through coding, categorized observations, annotated photographs, or maps.

Choose processing that suits the evidence, such as means, percentages, rates, spread, diversity indices, correlation, or significance testing. Complexity does not earn marks by itself. Show a sample calculation where useful, and do not hide evidence essential to the argument in an appendix.

Criterion E: Analysis and conclusion, 6 marks

Criterion E asks what the results mean. The 1-2 band identifies patterns but provides an unsupported or irrelevant conclusion. The 3-4 band describes patterns and gives some consideration to reliability, validity, bias, or uncertainty. For 5-6 marks, relevant patterns must be explained, data quality considered, and the research question answered directly using the analysis.

Do not stop at stating that nitrate concentration decreased downstream. Use processed values to establish the trend, then explain possible mechanisms such as dilution, plant uptake, microbial activity, or changing runoff inputs.

Reliability, validity, bias, and uncertainty are not labels to insert without discussion. Explain how natural variability, sampling decisions, measurement resolution, response bias, confounding variables, or source limitations affect confidence in the pattern. Conclusions should use proportionate language, such as “the evidence supports a moderate negative relationship,” rather than claiming that correlation proves causation.

Criterion F: Evaluation, 6 marks

Criterion F rewards critical reflection on limitations, improvements, and unresolved questions. For 1-2 marks, these points tend to be generic or merely stated. The 3-4 band describes relevant limitations and improvements and outlines further questions. For 5-6 marks, specific limitations and corresponding improvements must be evaluated in relation to their effects on the conclusion.

“Human error” is too vague. Explain the mechanism, such as sampling sites at different times, which introduced temperature and flow-rate variation that may have obscured the nitrate pattern. Pair each important limitation with a realistic improvement and explain how that change would strengthen reliability or validity.

Unresolved questions should emerge from the findings. You might ask whether the downstream trend persists during the wet season or whether phosphate follows the same relationship. These are stronger than unrelated suggestions for future research.

Common ESS IA marking mistakes

Strong reports maintain a clear connection from environmental issue to question, method, evidence, conclusion, and evaluation. Common problems include:

• Using the rubric from the course assessed through 2025.
• Providing background that does not justify the variables or question.
• Naming stakeholders without explaining their competing perspectives.
• Omitting sampling rules, intervals, controls, or database filters.
• Creating graphs without appropriate processing.
• Describing patterns without explaining environmental mechanisms.
• Mentioning uncertainty without judging its effect on the conclusion.
• Listing generic limitations and improvements.
• Treating a hypothesis as something that must be proved.
• Assuming more statistics automatically mean more marks.

Use the descriptors throughout drafting rather than checking them only at the end. The RevisionDojo ESS IA guide, current ESS IA rubric tool, and printable ESS IA checklist can support criterion-level review. Your teacher and official IB documentation remain authoritative for submission requirements.

Conclusion

The current ESS IA mark scheme rewards a coherent investigation, not perfect results. Criteria A-C establish the inquiry, strategy, and method; Criteria D-F reward correct data treatment, supported interpretation, and specific evaluation. Top-band work consistently moves from stating and describing to explaining and evaluating.

Before submitting, compare every section with its complete band descriptor. RevisionDojo's step-by-step ESS IA guide, ESS coursework exemplars, and rubric tool can help you review a complete draft systematically.

Sources and referenced URLs

• IB Environmental Systems and Societies subject brief, first assessment 2026
• IB Environmental Systems and Societies curriculum update
• IB assessment and moderation guide
• RevisionDojo ESS IA guide for the current syllabus
• RevisionDojo current ESS IA rubric tool
• RevisionDojo Criterion C method guidance
• RevisionDojo ESS IA checklist
• RevisionDojo step-by-step ESS IA guide
• RevisionDojo current ESS coursework exemplars