上 + (Modifier) + 课
上课 (shàngkè) is a separable verb meaning "to attend class" or "to have a lesson." Because it is separable, other elements such as aspect markers or modifiers can be inserted between 上 and 课, as in 上了一节课 (attended one class). When used without separation, it simply means "to go to class."
我每天早上八点上课。
Wǒ měitiān zǎoshang bā diǎn shàngkè.
I have class at eight every morning.
昨天我上了三节课,累死了。
Zuótiān wǒ shàng le sān jié kè, lèi sǐ le.
I had three classes yesterday and was exhausted.
老师还没来,我们还没开始上课。
Lǎoshī hái méi lái, wǒmen hái méi kāishǐ shàngkè.
The teacher hasn't arrived yet; we haven't started class.