Chris Meyer: “Stop teaching and help your students learn! An educational approach shared by Chris Meyer.” Also see the free high-school physics resources at this site.

JUMP Math: “Every child can learn math and love it. JUMP Math is a non-profit that empowers teachers to multiply the potential in every classroom through research-informed, curriculum-aligned resources and approaches that ignite and nurture an enduring understanding and appreciation of math in every student.”

Math Academy: “Math Academy offers a simple, gamified UI that makes it easy for students to get started quickly and without distractions.”

Khan Academy: “We’re a nonprofit with the mission to provide a free, world-class education for anyone, anywhere.”

mathcentre: “Mathcentre gives you the opportunity to study important areas of pre-university mathematics; the mathcentre team are a group of people who run university mathematics support centres, who teach mathematics, and who design new media products for learning.”

Mathigon: An interactive textbook that integrates active learning and deals with a variety of mathematics topics at about high-school level, particularly geometric ones.

MIT Highlights for High School: “Highlights for High School features MIT OpenCourseWare materials that are most useful for high school students and teachers.”

nRICH: “NRICH is an innovative collaboration between the Faculties of Mathematics and Education at the University of Cambridge which focuses on problem solving and on creating opportunities for students to learn mathematics through exploration and discussion. NRICH provides thousands of free online mathematics resources for ages 3 to 18, covering all stages of early years, primary and secondary school education — completely free and available to all.”

PhET: Interactive science simulations at the University of Colorado.

Purplemath: Algebra help, study skills, homework guidelines, and links.

Free STEM Resources Provided By Public Libraries: Free resources starting from elementary school all the way up to high school.

Students for Research: “Providing opportunities for high school and undergraduate students to understand the process of collecting, analyzing, and sourcing research.”