We develop the open learning platform serlo.org, which offers intuitive explanations, courses, videos, exercises and sample solutions for math and other subjects. K12 students use these to learn according to their individual needs and at their own pace. We strive to support especially those students all over the world, who can’t afford the additional private tutoring they would need to succeed in school. Serlo.org is completely free of charge, free of ads and we use open licences.