Who
California students, usually grades 6-12 locally and at CSEF by qualification. ISEF serves affiliated-fair finalists in grades 9-12; STS is senior-only.
Counselor intelligence brief
California Science Fair Guide
A California-only map of the science fair maze: local and county fairs, CSEF, Regeneron ISEF, Regeneron STS, grade eligibility, deadlines, and examples of projects that actually rose to the top.
Snapshot date 2026-05-25. Dataset: 3,111 parsed CSEF category-award rows plus 283 official award-source links.
Decision brief
California science fairs in five answers
What
A route map from school or district competition to the authorized county or regional fair, then potentially CSEF and Regeneron ISEF. STS uses a separate application.
When
School deadlines arrive before public fair dates. Confirm the student’s county route and current-cycle calendar before planning backward.
How
Look up the school county, confirm the authorized fair, secure required SRC approval before experimentation, and qualify through each affiliate-controlled stage.
Why
The route determines eligibility, approvals, deadlines, and access to state or international advancement. Starting with the wrong fair can close the pathway.
1. The pathway
Most California students start with the fair authorized for their school county. That fair may qualify projects to CSEF, to Regeneron ISEF, or to both.
Step 1
School or district fair
Optional or required by the local county. The student usually needs SRC approval before experimentation when humans, animals, microbes, hazardous agents, or regulated equipment are involved.
Step 2
County or regional fair
The practical gateway. LA County and OCSEF both accept grades 6-12 and are ISEF affiliates. Other counties route through their own CSEF affiliate.
Step 3
California Science & Engineering Fair
CSEF is the statewide fair. Students must qualify through an affiliated fair, and CSEF allocates a fixed number of project slots to each affiliate.
Step 4
Regeneron ISEF
ISEF finalists are selected by Society-affiliated fairs. CSEF can also name top senior winners as ISEF finalists.
Where Regeneron fits
The word "Regeneron" shows up in two different places. Regeneron ISEF is the international fair for grades 9-12, reached through an affiliated fair. Regeneron STS is a separate senior-only research competition for U.S. high school seniors. A California student can target both, but the calendars and applications are different.
2. County lookup
Choose the county where the student attends school. This uses CSEF's affiliate-by-county list, with each result linked back to the official CSEF affiliate page.
Pick a county to see the fair, grades, 2026 dates, and whether CSEF marks it as an ISEF affiliate.
LA County example
Los Angeles County Science & Engineering Fair: March 8 - March 9, 2026 | Awards Ceremony: Sunday, March 22. Grades 6 - 12. CSEF marks it as an ISEF affiliate.
LA County siteOrange County example
Orange County Science & Engineering Fair: March 11 - March 14, 2026 | Awards Ceremony: Sunday, March 22. Grades 6 - 12. CSEF marks it as an ISEF affiliate.
OCSEF site3. Grade eligibility
County and regional fairs
Usually 6-12
LA County and OCSEF list grades 6-12. Several California affiliates vary, so use the county lookup before advising a family.
CSEF
6-12 by qualification
CSEF receives qualified projects from affiliated fairs. CSEF's junior division feeds Thermo Fisher JIC; senior winners may be named ISEF finalists.
ISEF and STS
9-12 / seniors
ISEF is for high school finalists through affiliated fairs. STS is a separate senior-only application, usually due in November.
4. Deadlines and links
Exact school-level deadlines come earlier than the public fair dates. The dates below are the public 2026 fair dates visible as of May 25, 2026, plus the current ISEF event page.
| Program | Who | Public date | Link |
|---|---|---|---|
| CSEF 2026 | Qualified CA projects | April 11-12, 2026 | CSEF 2026 archive |
| LA County 2026 | Grades 6-12 in LA County | March 8-9, 2026; awards March 22 | CSEF affiliate page |
| OCSEF 2026 | Grades 6-12 in Orange County | March 11-14, 2026; awards March 22 | CSEF affiliate page |
| Regeneron ISEF 2026 | Affiliated-fair finalists | May 2026 in Phoenix, Arizona | ISEF page |
| Regeneron STS | U.S. high school seniors | Annual application, usually November | STS page |
5. Winner examples worth studying
A useful archive should show what strong projects look like, not merely who won. These 2026 examples come from CSEF's Major Fair Awards PDF and are paired with the category-award records parsed for this site.
2026 Senior Project of the Year S-17-03 Physics & Astronomy
Orbital Reconstruction and Discovery of Hidden Circumbinary Planets through Eclipse Timing Residuals and N-Body Dynamics
Elizabeth Zhang, grade 11. The Harker School, Santa Clara County.
A math-heavy astronomy project with a specific discovery claim. Strong signal: advanced modeling attached to a concrete astronomical target.
2026 Junior Project of the Year J-15-02 Medicine & Physiology
Modulation of Pseudomonas fluorescens Biofilm and Quorum Sensing Pathways by Natural and Synthetic Inhibitors
Rene Kwon, grade 8. Sierra Vista Middle School, Orange County.
A junior project that still reads like real experimental biology. Strong signal: mechanism, organism, and intervention are all explicit.
2026 ISEF finalist S-02-25 Applied Mechanics
Kiri-Grip: Integrated Kirigami-EMG Robotic Hand with Geometric Optimization of Cut Topologies for Assistive Grasping
Serena Yuan, grade 9. Menlo School, San Mateo County.
A build-oriented engineering project with a user-facing assistive purpose. Strong signal: physical prototype plus optimization language.
2026 ISEF finalist S-04-34 Biochemistry / Molecular Biology
Defining 3D Phenotypic Cell States of Polymorphonuclear Neutrophils via Novel Computational Pipeline
Emma Liu, grade 11. The Bishop's School, San Diego County.
A computational pipeline framed around biological state definition. Strong signal: method contribution plus a biomedical object of study.
2026 ISEF finalist S-05-09 Chemistry
Renewable Ammonia Electrochemical Synthesis by Glow Discharge with an Iron Based Catalyst
Ihan Sung, grade 11. Eastlake High School, San Diego County.
A clean-energy chemistry project with materials and synthesis details in the title. Strong signal: measurable process improvement.
2026 ISEF finalist S-08-18 Earth & Environmental Sciences
Physics-Anchored Short-Term Earthquake Hazard Characterization Using Large-Scale Seismic Data
Hao Lin, grade 11. Mira Costa High School, Los Angeles County.
A data project made stronger by physical grounding. Strong signal: large public dataset plus domain constraints, not generic prediction.
2026 ISEF finalist S-12-05 Environmental Engineering
Autonomous Drone-Based Early Detection and Precision Control of Wheat Diseases
Shreyan Mitra, grade 11. California High School, Contra Costa County.
An applied field problem with sensing, autonomy, and intervention. Strong signal: detection is paired with a plausible control loop.
2026 ISEF finalist S-14-05 Mathematical Sciences
The Repelling Propellers Problem: Optimizing Energy Configurations in Orbital Patterns
Riya Mehrotra, grade 11. Los Altos High School, Santa Clara County.
A theoretical project with a memorable mathematical object. Strong signal: clear optimization problem, not just broad mathematical interest.
How to use these examples
Study the project shape: specific system, measurable method, real-world constraint, and a title that makes the contribution legible. Do not treat the categories as a recipe list. CSEF rewards different kinds of excellence across junior, senior, theoretical, computational, experimental, and engineering projects.
Archive search
The searchable archive is still useful for school, county, category, and year patterns. It is an award ledger, not a complete project-abstract library.
| Year | Student | School | County | Award |
|---|
Latest parsed year: 2026
255 parsed category-award rows from 2026. Category rows are student-level, so team projects appear once per student.
Most represented counties
- Santa Clara515
- Los Angeles425
- San Diego371
- Orange318
- Unknown240
- San Mateo147
- Riverside125
- Fresno122
- Alameda105
- Santa Cruz101
6. Strategy notes from the archive
Start with forms, not slides
Projects involving people, animals, microbes, tissue, chemicals, drones, radiation, or controlled equipment need approval before the work begins. Late paperwork can erase an otherwise strong project.
Win the local gate
CSEF allocations count projects. A three-student team uses one project slot, but every teammate still needs clean paperwork and a clear role.
Choose categories with care
The same idea can land differently as computational systems, environmental engineering, behavioral science, or medicine. Category choice decides the judge pool and the comparison set.