Is 如果我们，所有的学生，没有我们的中文老师，我们就永远不能站起来在听众前面说中文 grammatical and does it makes sense?
如果没有老师，我们——所有学生——就绝不可能在听众面前说中文。


I think that "all the students" must be translated and not omitted; here it is used for emphasis.  And "would never be able to " is 绝不可能。