Revised 10 November 2026 · v1.2.0 · what changed

"Solve the last five years' papers" is close to universal advice from CBSE coaching material. It is also, on the evidence, true for some subjects and nearly meaningless for others. A parse of 1,955 Class-XII question papers from cbse.gov.in (2022–2026, main and compartment sittings, 30,734 questions extracted) can measure this directly: for each subject, what share of the high-mark (≥4-mark) marks sit on a topic — a 2–4-word phrase — that recurs across at least three of the five exam years. Call it the repetition index.

The repetition index, by subject

The split does not track how big a subject's syllabus is. It tracks how formulaic its questions are — and that is a very different sort by subject than most study advice assumes:

What actually recurs, and where

Accountancy is the most repetitive paper in the corpus. Two topics alone — admission/retirement of a partner (14 papers across 2023/25/26, 139 marks) and the balance sheet incl. Common Size Balance Sheet (20 papers across 2024/25/26, 139 marks) — plus profit-sharing-ratio changes, cash flow from investing activities, and dissolution of the firm make up most of the high-mark paper, year after year.

Physics has exactly two topics that recur at high marks in 4 of the 5 years, across the entire 11-subject corpus: electric field (14 papers, 84 marks) and magnetic field (11 papers, 73 marks). Parallel-plate capacitors and refractive index follow at 3-of-5 years. No other subject has a single content topic that reliable.

Economics leans on a recurring numerical format — the “for a hypothetical economy, it is known that…” problem appears in 14 papers worth 133 marks — plus aggregate demand, commercial banks/RBI, and gross value added. History circles a small set of sourced narratives (Vijayanagara Empire, Quit India Movement, Salt Satyagraha, Bombay Deccan riots) even though its index reads a modest 16%, because those set-pieces sit specifically in the 8-mark long-answer slot. Business Studies reuses “functions of management” (planning, directing) almost verbatim across three straight years.

A separate finding: the same skill-subject block, six times over

Away from topic recurrence, the corpus's structural analysis turns up a more actionable pattern for students taking any of CBSE's Skill Education electives (Artificial Intelligence, Information Technology, Web Applications, Taxation, Financial Markets Management, Typography & Computer Applications). Every one of these papers devotes roughly 10 of its 50–60 marks — 17–20% — to an identical five-unit Employability Skills block: communication, self-management, ICT basics, entrepreneurship, and green skills. The wording repeats near-verbatim across subjects — the same active-listening question appears in both the Taxation and Web Applications papers; the same “Ctrl+M adds a slide” item appears in both AI and Typography.

Does this hold over more years? Ten years of official sample papers say: mostly, yes

The repetition index above is built on five years of administered exam papers (2022–2026) — cbse.gov.in itself does not publish real Class-XII papers from earlier sessions in a form this analysis could fetch. But CBSE separately publishes an official Sample Question Paper (SQP) before each session, illustrating that year's format and a slice of its content, going back to 2015-16. Searching that decade-long SQP archive for the specific topics already found recurring in the real-paper analysis gives an independent, longer-run check on the same claim:

Physics's two field topics and Economics's “aggregate demand” check out in every single sample paper CBSE has released in the last decade — a far stronger confirmation than the original 4-of-5-years finding, and evidence that this isn't a quirk of the 2022–2026 window. Accountancy's broad “balance sheet” topic is equally universal. But the specific partnership-admission/retirement cycle that dominates Accountancy's high-mark real-exam questions (14 of 20 papers across three exam years) shows up in only 2 of 7 sample papers.

What would break this analysis

The takeaway

"Practise past papers" is not one piece of advice; it's eleven, and they don't agree. For Accountancy and Physics students, five years of past papers genuinely rehearse a large share of what will be asked again — and for Physics and Economics specifically, a decade of official sample papers backs that up further still. For English Core, Biology, and Chemistry students, the same advice mostly teaches format and timing, not content, because those subjects are built not to repeat. And for anyone taking a Skill Education elective, the highest-certainty ten marks in the entire paper are a shared syllabus block that has nothing to do with the subject's name.

Use the tool yourself

Note, 11 November 2026: the CBSE_paper_patterns repository has since been made private, so the clone commands below no longer work for readers. The figures in this post are unchanged.

The analysis comes from the CBSE_paper_patterns repository. You do not need to rebuild the corpus to check the figures: the repository ships the derived tables in data/, and reading them needs only Python’s standard library. A video walkthrough shows the same steps.

git clone --depth 1 https://github.com/herrrickshaw/CBSE_paper_patterns.git
cd CBSE_paper_patterns

# the repetition index by subject (subject, papers, index %)
python3 -I -c "import csv;[print(r['subject'],r['papers'],round(float(r['repetition_index'])*100)) for r in csv.DictReader(open('data/subject_repetition.csv'))]"

# the recurring content topics for one subject (phrase, years, papers, marks)
python3 -I -c "import csv,sys;[print(r['phrase'],r['year_list'],r['papers'],r['marks']) for r in csv.DictReader(open('data/recurring_topics.csv')) if r['subject']==sys.argv[1] and r['kind']=='content_topic']" Physics

The first command prints the eleven subjects with the index in the table above (Accountancy 49, Physics 44 and so on). The second, for Physics, starts with electric field (2023 to 2026, 14 papers, 84 marks) and magnetic field (11 papers, 73 marks). Swap Physics for any subject. The repository also holds question_type_mix.csv, paper_structures.csv and syllabus_vs_actual.csv for anyone who wants to go further, and the analysis notes explain three traps for parsing CBSE PDFs: reprinted options, Hindi-medium text that extracts as mojibake, and exam sets counted as separate papers.

Sources: 1,955 CBSE Class-XII question papers, main and compartment sittings, downloaded directly from cbse.gov.in/cbsenew/question-paper.html, academic years 2022–2026; 30,734 questions parsed (16,633 usable English-medium text), extracted with pdftotext -layout and mined for 2–4-word recurring phrases (n-grams appearing in ≥3 of 5 exam years, boilerplate stripped). Paper-architecture detail (Employability Skills block, section structure) from a separately reconciled 32-paper 2024-25 subset whose marks were checked against each paper's own General Instructions. The ten-year extension uses CBSE's own Sample Question Paper archive (cbseacademic.nic.in, sessions 2015-16 to 2024-25, sourced from this account's corpus), searched directly for the phrases already found recurring in the real-paper analysis — a targeted presence check, not an independent re-mining of the SQP text. cbse.gov.in and cbseacademic.nic.in could not be fetched directly from this piece's research environment for anything beyond what the underlying repository already held; no post-2024-25 SQP or pre-2022 real exam paper is claimed here that was not already in that corpus. Full analysis, methodology and the underlying DuckDB tables are documented in this account's own CBSE_paper_patterns research repository; the “Use the tool yourself” commands were run against its data/subject_repetition.csv and data/recurring_topics.csv on 10 November 2026.

What would fix this

• CBSE should publish Hindi-medium question papers with Unicode-encoded text rather than legacy embedded fonts, so that Hindi-medium papers, which currently extract as unreadable characters, can be analysed alongside the English-medium ~54% of questions this piece was able to use.
• CBSE should restore its archive of administered Class XII question papers from before 2022 on cbse.gov.in, in downloadable form, so that recurrence claims can be tested on real papers over a decade rather than relying on one sample paper per session as a proxy.
• CBSE should release a machine-readable file with each paper listing every question’s marks, section and syllabus unit, so that marks no longer have to be parsed heuristically from paper text and any repetition index can be computed exactly rather than to within a few percentage points.
• CBSE should publish a subject-wise statement each year of how high-mark questions were distributed across syllabus units in the main and compartment sittings, so that students get evidence on which subjects reward past-paper practice instead of uniform coaching advice that fits Accountancy and not English Core.

These are proposals from this blog, not recommendations any agency has adopted.

About this article: Researched, written and edited by Umashankar Triplicane Dwarakanathan, with AI research assistance; every figure is meant to trace to the primary source cited. See the Editorial Policy for how sourcing, AI use and corrections work.