英文既解釋 幫幫手

...........Gates’parents placed him into Lakeside, an “academically challenging”private school. .........

1. academically challenging 點解??

...........Richard Williams did not let Venus or Serena play competitively until they were late into their teens. Some coaches warned him he was “throwing away their careers”with this attitude, but when Venus ......

2. throwing away their careers 點解??
係咁多la....我想要中文解釋。唔該了！