American high-schoolers are earning more credits and taking more challenging courses than they did 20 years ago, according to a new study of high school transcripts. But education experts still worry that not enough of them are graduating ready to enter college or get on track for science- and math-based careers.

Almost twice as many students completed at least a standard curriculum in 2009 as in 1990, the report shows. Curricular rigor improved for students across racial and ethnic groups, but significant gaps still remain.

The economic future of the country depends on improving education, and “the message [of this study] is that rigor works,” says Bob Wise, president of Alliance for Excellent Education in Washington, which advocates for improving high schools. “But it puts an obligation on all of us to be sure we’re not only providing rigorous courses, but also the support students need to succeed in them.”

Tracking student coursework is important, policymakers say, because some research has shown that a more challenging curriculum is associated with success in education beyond high school. Today’s study comes at a time when the vast majority of states are moving toward a set voluntary Common Core State Standards designed to teach students at a more demanding level.

Key findings from the national report card

Among the key findings comparing 2009 with 1990, in the study released today by the National Assessment of Educational Progress (NAEP):

• Students received an average of about 420 more hours of instruction, primarily through summer school and online courses.
• 75 percent of high school graduates completed at least a standard curriculum (including four credits of English and at least 3 credits in social studies, math, and science). That’s up from 40 percent.
• 46 percent completed a mid-level curriculum (which adds the requirements of algebra II or geometry, one foreign language credit, and two courses out of biology, chemistry, and physics). That’s up from 26 percent.
• 13 percent completed a rigorous curriculum (which adds the requirement of a credit in pre-calculus or a higher course in math, all three of the above science courses, and two more credits in a foreign language). That’s up from 5 percent.
• Those completing a rigorous curriculum had the highest average NAEP achievement scores.
• Grade-point averages rose from 2.68 to 3.00, but have not changed significantly since 2005.

“This study confirms that we need higher secondary standards across the board. In particular, we need stronger requirements in math and science,” said David Driscoll, chair of the National Assessment Governing Board, in a written statement. The board sets policy for NAEP, a project of the US Department of Education.

One area that math-education reformers have been pushing is an earlier emphasis on algebra, considered a gateway course for higher-level math and science. Those efforts appear to be bearing fruit. In 2009, 1 in 4 high school graduates had taken algebra I before high school, up from 1 in 5 in 2005.

Geometry usually comes after algebra, and those who started high school in a geometry course scored 31 points higher on the 2009 NAEP math assessment than those who started high school in algebra I.

Persistent achievement gaps

For those who track the achievement of various subgroups of students, the study revealed both progress and persistent gaps.

The portion of African-American graduates who completed a below-standard curriculum decreased from 60 percent in 1990 to 21 percent in 2009. But while 14 percent of white high school graduates had a rigorous curriculum in 2009, that held true for only 6 percent of African-Americans and 8 percent of Hispanics.

“African-American and Latino students are still less likely to attend high schools that offer high-level math courses like trigonometry and calculus, which severely limits their ability to take the courses they’ll need to be successful,” said Kati Haycock, president of The Education Trust, in a statement. The Washington policy group works to close racial and income-based achievement gaps.

Also more likely to complete a below-standard curriculum, today’s study showed, were students with a parent who did not finish high school (34 percent), English-language learners (63 percent), and students with disabilities (45 percent).

For more students to gain from strong math and science courses, particularly in urban areas where minority and low-income students are often concentrated, “the bottom line is we need to increase the quality and rigor of teacher training,” said Henry Kranendonk, a math curriculum consultant to the Milwaukee Public Schools and a member of the National Assessment Governing Board.

It’s also a costly proposition, Kranendonk noted, for cash-strapped school districts to find ways to offer high-level courses, especially in schools where the number of students ready for such courses is small.

Ensuring that all students take more challenging courses “will require resources, but there’s a definite return on investment when you do it,” says Wise of the Alliance for Excellent Education.

The study, America’s High School Graduates, Results of the 2009 NAEP High Scho..., is based on a nationally representative sample of 37,700 public and private high school graduates nationwide, compared with several previous samples dating back as far as 1990.