Each grade act as a step in the whole staircase to the mathematics high_rise building. Performing poor in math in any grade is like breaking some steps in the whole staircase. As broken steps make the whole staircase risky or scary to use in the future, incomplete math competencies in lower grades make math very hard in the high school. So, what it takes to be smart in mathematics? My answer is; stay focused on math in each and every level of your studies. Participate in your class math practice sessions. Ask your teacher lots of questions until you are not clear about any concept. Mathematics is a subject of solving the problems on paper by hand rather than only to read them. As in case of Social Studies taking more readings make you smart, in math practicing lots of problems and solving them by hand makes you smart. To practice mathematics, math workbooks are the good source. You learn a concept in a workbook, then in the same booklet there are more problems on the same concept for practice. Another good method to practice mathematical concepts is using math worksheets and you can print math worksheets free of charge from the web.
There are some new materials being developed now based on what we are learning about how the brain learns. These brain_friendly materials should be an improvement over what has existed. I recently bought a book by Marcia L. Tate titled "Mathematics Worksheets Don't Grow Dendrites." I highly recommend her book. She gives a great deal of information on alternative activities that are better for your child's brain development and for learning.