The myth is that Einstein failed mathematics, which is easily debunked. His final grades from Aargau Kantonsschule show that Einstein received top marks in mathematics. Einstein did poorly in French, but he didn't fail.

Subject | Grade :--:|:--:|:--: German | 4-5
French | 3 English | - Italian | 5 History | 5 Geography |4 Algebra | 6 Geometry | 6 Descriptive geometry | 5 Physics | 5-6 Chemistry | 5 Natural history | 5 Artistic drawing |4 Technical drawing | 4

But the question being posed here is whether Einstein had failing grades, and that's another matter. Einstein did receive failing scores, but it was as a university student studying physics at the Eidgenössische Technische Hochschule (ETH). The professor for both classes, Jean Pernet, flunked Einstein for failing to attend his courses. Einstein scored a 1 in Pernet's Physics Practice for Beginners class in his third year and a 1 in Pernet's Physics Experiments for Beginners class in his fourth year. For further reading see The Collected Papers of Albert Einstein. Volume 1; The Early Years: 1879-1902. Anna Beck, Translator; Peter Havas, Consultant. Princeton, NJ: Princeton University Press, 1987.