Xiao Ming goes to an English cram school outside school every weekend. Xiao Qiang has never attended an English cram school. As a result, Xiao Ming and Xiao Qiang scored 95 and 55 respectively in the final exam. 
The teachers in English cram schools don't teach very carefully
 the reason why Xiaoming's English is better than Xiaoqiang is that he went to an out-of-school cram school.