A high school diploma has become vital to career and financial success, and the U.S. high school graduation rate has climbed higher than ever before.

As educators work to get even more students into caps and gowns, they are experimenting with innovative instructional methods. Through specialized class work, high schools are facilitating teen entrepreneurs and published authors, for example. Plus, there has been a renewed interest in career and technical programs.

Many different kinds of schools are among those recognized in the 2015 Best High Schools rankings, released today. U.S. News looked at more than 29,000 public high schools in all 50 states and the District of Columbia to determine which schools excelled in each state and nationally.

Explore the Best High Schools national rankings. ]

For the fourth consecutive year, the School for the Talented and Gifted, a Dallas magnet school known as TAG, was ranked as the No. 1 public high school in the country.

Principal Ben Mackey says high expectations and a supportive environment are among the keys to running a successful high school. His school enrolls about 250 students – roughly 60 per grade.

"We are a small school and we believe very passionately that that is one of our major things that sets us apart," he says. "It allows us to really build and create a familial culture where I as a principal know every single student by more than just their name."

BASIS Scottsdale in Arizona took second place in the national rankings for the second year in a row, but there was movement elsewhere in the top 10.

The School of Science and Engineering Magnet in Texas – located in the same facility in Dallas as TAG – climbed further up the top 10. It took the No. 5 spot after placing eighth in 2014.

To create the 2015 Best High Schools rankings, U.S. News worked with RTI International, a North Carolina-based research firm. High schools were evaluated in three stages.

First, U.S. News looked at overall student performance on state-required tests. Schools had to perform better than average to pass, but because of a slight change to the methodology this year, more schools qualified for the rankings.

Then, U.S. News factored in how effectively schools educated their least-advantaged students – those of black, Hispanic and low-income backgrounds. Finally, schools were assessed on how well they prepared students for college based on participation in and performance on Advanced Placement and International Baccalaureate exams.

In the national rankings, 500 high schools received gold medals, 2,027 schools earned silver and 3,990 took home bronze.

Along with the rankings, U.S. News has published data on more than 21,100 public high schools, which parents can use to help identify the right school for their child. The ​information includes student demographics and results on statewide assessments, as well as AP and IB exams.

Out of all the states, Maryland performed best overall in the Best High Schools rankings. Nearly 30 percent of its eligible high schools earned gold or silver medals.

Second to Maryland was California, where slightly more than 27 percent of eligible schools were awarded gold or silver.​

On the other end of the spectrum, no schools received gold or silver medals in Alabama and South Dakota. Those states did not give U.S. News permission to use their schools' AP data. ​

Among the top 500 high schools nationally, 178 were charter and magnet schools. U.S. News has also published separate rankings of these types of schools, both of which usually limit enrollment. Charter schools typically have more flexibility in their ​operations than traditional public schools. Magnet schools often attract more academically talented students.

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BASIS Scottsdale topped the 2015 Best Charter Schools rankings​, followed by Gwinnett, in a repeat of last year​. ​Two California schools are new to the top five, American Indian Public High School in third and Pacific Collegiate School in fifth.

Three nationally ranked Texas schools led the Best Magnet Schools rankings: TAG, the School of Science and Engineering Magnet and Carnegie Vanguard High School.

Additionally, U.S. News determined the Best High Schools for STEM – science, technology, engineering and mathematics – using data on participation in and performance on AP tests in math and science.

Schools had to be awarded gold in the national rankings to be considered; 250 schools were ranked for their STEM performance.

High Technology High School in New Jersey took the No. 1 STEM high school spot back from Thomas Jefferson High School for Science and Technology, which fell to No. 2. Prior to 2014, High Technology High School had been the top STEM high school for three years.

BASIS Scottsdale,​ Middlesex County Academy for Science, Mathematics and Engineering Technologies ​in New Jersey and Whitney High School ​in California rounded out the top five STEM high schools.