Students with foreign background do not reach the goals of mathematics education in the Swedish school to the same extent as students with a Swedish background, this is shown in a number of Swedish and international reports. Both Swedish and international research show that it takes many more years to learn a language so well that the student is capable of learning new school-related knowledge in this new language than just using the language for everyday speech. Students with foreign background are in danger of falling far behind their peers in school in for example mathematics where they language-wise are not able to acquire knowledge. One method for helping students with another native language than Swedish is to provide mathematics education in two languages, Swedish and the student's native language. In media a number of politicians have expressed negative and positive arguments about this method, the opponents have argued that the students' Swedish skills would be suffering. I have chosen to compare a school applying bilingual mathematics education and one which instead is working with a so-called study workshop (studieverkstad). This study focuses on grades in mathematics from grade 9 and results from the national tests in mathematics in grade 9, and two interviews with teachers, one teacher of mathematics and one mother-tounge language teacher. I have chosen to study grade and test statistics from these two schools during several years to see what effect is acquired by each method of working. The main finding of this study is that bilingual mathematics teaching tends to keep students' grades at a constant level while students' grades decrease when using the study workshop method.