While there were some shared general features, there was discernible variation across the countries in teaching eighth-grade mathematics. Distinctions included the introduction of new content, the coherence across mathematical problems and within their presentation, the topics covered and the procedural complexity of the mathematical problems, and classroom practices regarding individual student work and homework in class.

A sample of these findings is summarized below.

Eighth-grade mathematics lessons in the Czech Republic placed a greater emphasis on reviewing previously learned content than those in all of the other countries except the United States; lessons in Japan placed a greater emphasis on introducing new content than those in all six of the other countries; placed a greater emphasis on practicing new content than those in the Czech Republic, Japan, and Switzerland.

	Figure 1 Average percentage of eighth-grade mathematics lesson time devoted to various purposes, by country: 1999 1Japanese mathematics data were collected in 1995. 2AU=Australia; CZ=Czech Republic; HK=Hong Kong SAR; JP=Japan; NL=Netherlands; SW=Switzerland; and US=United States. 3Practicing new content: HK>CZ, JP, SW. 4Introducing new content: HK, SW>CZ, US; JP>AU, CZ, HK, NL, SW, US. 5Reviewing: CZ>AU, HK, JP, NL, SW; US>HK, JP. NOTE: For each country, average percentage was calculated as the sum of the percentage within each lesson, divided by the number of lessons. Percentages may not sum to 100 because of rounding and the possibility of coding portions of lessons as "not able to make a judgment about the purpose." SOURCE: U.S. Department of Education, National Center for Education Statistics. Third International Mathematics and Science Study (TIMSS) 1999 Video Study. (Originally published as figure 3.8 of the report from which this highlights summary is drawn, Teaching Mathematics in Seven Countries: Results From the TIMSS 1999 Video Study [NCES 2003-013]).

Although, on average, eighth-grade mathematics lessons in all of the countries included some time reviewing previous content and some time introducing and practicing new content, there were differences in emphases in each country. Combining the time spent on both introducing and practicing new material provides another way of detecting differences: Australia, Hong Kong SAR, Japan, the Netherlands, and Switzerland devoted more time, on average, to studying new content (ranging from 56 to 76 percent of lesson time) than reviewing previous content; the Czech Republic spent more time, on average, reviewing previous content (58 percent of lesson time) than studying new content; and in the United States there was no detectable difference between the average percent of lesson time devoted to reviewing previous content and studying new content (53 and 48 percent of lesson time, respectively). Moreover, while a single mathematics lesson could combine time spent reviewing and introducing and practicing new content, there were a number of lessons that were entirely devoted to just one of those purposes. In the Czech Republic and the United States, a greater percentage of eighth-grade mathematics lessons were spent entirely in review of content previously presented than in Hong Kong SAR and Japan (28 and 28 percent of lessons compared to 8 and 5 percent, respectively).