Couple of major flaws:
1) Did not include asians as a minority. There is definitely a very significant participation among that ethnic group. They did not count them at all!
2) Like schang said, this study only shows a LINK between better academic achievement and tennis participation. It should not jump to the conclusion that tennis CAUSES better academics, aspirations, etc. It could just be that the kids that play tennis already have better academics and aspirations, etc. because they come from (as the study has shown) higher socioeconomic backgrounds and college-educated parents.
Finally, as the report itself concludes:
"Tennis is neither a cause nor an effect in relation to educational advancement..."