楼上的也太那个点了吧,直接用翻译工具翻译整句话,牛x.
楼主的句子不全,把所有的关掉是关掉什么东西?电器吗?没写宾语啊
以下两个仅供参考：
Make sure that turn off all the appliances when you leave the classroom.
Make sure all the appliances being turned off when you leave the classroom.