During the period of school don't surf the Internet，在校期间不要上网。或者During the period of school not to the Internet 。Please do not use internet during school time。这个就是祈使句了，表示希望或者请求。如果是命令的话，最好使用上面两个。Surfing the Internet is not allowed in school。学校是不允许上网的。希望对您有帮助。希望被采纳，3Q。！
芳儿beauty
