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 a searchable dataset of public CSEF award records.
Snapshot date 2026-05-25. Dataset: 3,111 parsed CSEF category-award rows plus 283 official award-source links.
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.
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. Past winners dataset
Search parsed public CSEF category-award records. Each record links back to the official award file for that year. The full JSON and CSV are available for download.
| 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.