What is the difference between 课 and 班级? Is there any difference between 课 and 班级? As far as I know, both mean class in school. Some of example sentences I read are below:

这个班级上数学课的时候用计算机
他正在准备历史课的作业
这是一个高中的班级
他们正在上法语课
我的班级是在学习念英文
我想要教画画课


It might look like that the 课 means a class that represents any specific subject, while the 班级 means a class in general. First, is this true? And second, is there any difference aside from that? 

I also want to know that, if you want to express "Let's go to the class!" in Mandarin, which one should I use? And if I use the wrong one, does it still make a reader get the meaning or does it carry completely different meanings?
班级 is a group of students who started school in the same year and participate in classes together, it's the students themselves. 

课 is a unit of the curriculum, that is held by a teacher, professor and is attended by the students.