我认为应该这样改：
In the past,teachers always kept explaining (the points可以舍弃) in class and our students just listened and took notes.But now we often discuss and try to solve the problems raised by the teachers by ourselves.
过去,都是老师在课堂上一个劲地讲（ kept explaining ）,学生边听边做笔记 （our students just listened and took notes）.而现在,我们经常独自（by ourselves）来讨论、动脑筋解决（ try to solve ）老师提出的（raised by the teachers）问题（the problems ）.
你觉得如何?