17 academic discussion 5% more time per day than poorer students.<sup>82</sup> The study estimated that students of low socioeconomic levels would need to attend school 1.5 months during the summer break in order to attain an equivalent amount of engaged learning time. Wastage adds up over the years and creates risks for poorer students.

Although research has been ex post facto rather than experimental, the relationship between instructional time and student achievement has been consistently positive.<sup>83</sup> For example, an extensive review of U.S. studies concluded that other things being equal, the amount learned is generally proportional to the time spent in learning.<sup>84</sup> Variables measuring curricular exposure are strong predictors of test scores<sup>85</sup> and correlations between content exposure and learning are typically higher than correlations between specific teacher behaviors and learning.<sup>86</sup> These positive relationships have been fairly consistent in studies employing different analytical perspectives, measurement strategies and units of analysis.<sup>87</sup> Two comprehensive reviews of research on learning effects demonstrated the positive influence of time on learning and the increasing precision in defining it: in an earlier review of 35 studies positive effects were found in 30 (86%) of the cases; in a later review of more than 100 studies positive influences were seen in 88% of the studies.<sup>88</sup> The association between time and learning was weakened only when other classroom factors were controlled, such as student differences in aptitude and prior knowledge, differences in the quality of classroom instruction and morale, or properties related to pupils' socio-economic environments.<sup>89</sup> Research outside the U.S. has been sparse. More instructional time spent on general science was associated with higher academic achievement in Iran, India and Thailand.<sup>90</sup> Increased pupil reading time had a positive effect on pupil achievement in Chile and India. School-based instructional time was found to be especially significant for children who got little school academic engagement after school hours.<sup>91</sup> Instructional time was found to be one of three major areas (in addition to teacher quality and textbook availability) in which consistent achievement effects were obtained.<sup>92</sup> In a review of 14 studies involving instructional time in developing countries, 12 studies showed a positive relationship between instructional time and student achievement. Another study examined the influence of a variety of active learning methods and found instructional 82. Greenwood 1991 83. Bloom 1971; Fisher and Berliner 1985; Gettinger 1984, 1989; Rosenshine 1979; Walberg 1988; Wang 1998; Wiley and Harnishfeger 1974 84. Frederick and Walberg 1980, 85. Content exposure was the most significant predictor of written test scores after everything else was controlled, while quality of instructional delivery was the most significant predictor of hands-on test scores. Further, students' attendance rate, content coverage, content exposure, and quality of instructional delivery are significant predictors of students' achievement test scores. (Wang 1998, p. 150) 86. Rosenshine 1979 87. Huyvaert 1998 88. Walberg and Fredrick 1991 89. Walberg 1988; also Worthen et al. (1994) found that the learning effects of increased time may be overstated.

90. Heyneman and Loxley 1983. In rural India student achievement was higher in schools with more instructional time; schools teaching the highest number of hours reported 66 more hours per year than schools with lower achievement (World Bank 1997).

91. See Suryadi, Green and Windman (1981) in Lockheed and Verspoor 1992.

92. Fuller and Clarke 1994