U.S. TIMSS Science Scores Over Time: 1995–2023
U.S. science achievement in the Trends in International Mathematics and Science Study is available across seven Grade 4 cycles and eight Grade 8 cycles through 2023. The two grade levels use separate TIMSS science scales and are tracked independently over time.
U.S. Science Trend Snapshot
Latest averages and NCES long-run comparisons for the two U.S. grade-level science series.
Grade 4 and Grade 8 Science Trends
Separate charts preserve the grade-level scaling used by TIMSS. The fixed 500 centerpoint is a scale reference, not a 2023 international average.
Grade 4 Science Scores, 1995–2023
U.S. average scale score across every available Grade 4 TIMSS science cycle.
Grade 4 was not administered in TIMSS 1999. NCES reports the 2023 average as 9 points lower than 1995 using unrounded estimates, although the published rounded scores are 542 and 532.
Grade 8 Science Scores, 1995–2023
U.S. average scale score across all eight Grade 8 TIMSS science cycles.
The 2023 Grade 8 average of 513 was not measurably different from either the 2019 average of 522 or the 1995 average of 513.
All U.S. TIMSS Science Trend Points
Published average science scores for every available U.S. Grade 4 and Grade 8 assessment cycle from 1995 through 2023. The comparison column reflects the NCES test against the 2023 estimate.
| Year | Grade | Average Score | Comparison With 2023 |
|---|---|---|---|
| 1995 | 4 | 542 | Measurably higher |
| 1995 | 8 | 513 | No measurable difference |
| 1999 | 8 | 515 | No measurable difference |
| 2003 | 4 | 536 | No measurable difference |
| 2003 | 8 | 527 | Measurably higher |
| 2007 | 4 | 539 | No measurable difference |
| 2007 | 8 | 520 | No measurable difference |
| 2011 | 4 | 544 | Measurably higher |
| 2011 | 8 | 525 | Measurably higher |
| 2015 | 4 | 546 | Measurably higher |
| 2015 | 8 | 530 | Measurably higher |
| 2019 | 4 | 539 | No measurable difference |
| 2019 | 8 | 522 | No measurable difference |
| 2023 | 4 | 532 | Reference year |
| 2023 | 8 | 513 | Reference year |
How the Science Score Distribution Shifted
Selected 2015 and 2023 percentile scores show whether movement in the national average was concentrated near the lower or upper end of the U.S. score distribution.
| Grade | Year | 10th Percentile | Average | 90th Percentile | 90th–10th Gap |
|---|---|---|---|---|---|
| 4 | 2015 | 439 | 546 | 644 | 205 |
| 4 | 2023 | 404 | 532 | 645 | 241 |
| 8 | 2015 | 421 | 530 | 631 | 210 |
| 8 | 2023 | 385 | 513 | 634 | 249 |
Lower-end movement widened the score spread
- At Grade 4, the 10th-percentile score moved from 439 in 2015 to 404 in 2023, while the 90th-percentile scores were 644 and 645. The 90th–10th gap increased from 205 to 241 points.
- At Grade 8, the 10th-percentile score moved from 421 to 385 over the same period, while the 90th-percentile scores were 631 and 634. The gap increased from 210 to 249 points.
- NCES marks the 2015 10th-percentile scores and score gaps as measurably different from their 2023 estimates at both grades; the 90th-percentile endpoints are not marked as measurably different.
TIMSS Data Sources and Measurement
National Center for Education Statistics, TIMSS 2023 U.S. Results, including U.S. science trend figures S5a and S5b.
International Association for the Evaluation of Educational Achievement, Trends in International Mathematics and Science Study.
U.S. Grade 4 and Grade 8 science achievement from 1995 through 2023. Grade 4 TIMSS was not administered in 1999.
Scores are reported on a 0–1,000 scale. Each TIMSS grade-and-subject trend scale has a fixed centerpoint of 500 and a standard deviation of 100 on the original 1995 metric.
Successive TIMSS cycles are linked through common assessment items so achievement can be compared across years within the same grade and subject.
Published chart values are rounded, while NCES comparisons use unrounded estimates. For Grade 4, the displayed 1995 and 2023 scores are 542 and 532, but NCES reports the long-run change as 9 points.
NCES reports cycle-specific sampling and population-coverage qualifications for U.S. TIMSS estimates. Small score differences should be interpreted with the corresponding technical notes rather than from rounded subtraction alone.
Average scores and percentile values are descriptive estimates of U.S. student achievement. A lower or higher value does not by itself identify the cause of a change. NCES statistical comparisons, rather than subtraction of rounded chart labels alone, determine whether two estimates are measurably different.
TIMSS scales Grade 4 science and Grade 8 science separately. A Grade 4 score of 532 and a Grade 8 score of 513 therefore cannot be subtracted to measure learning between grades. Direct trend comparisons are valid within the same grade-level science series across assessment cycles.