Can you get into night school if your in middle school?

Depends on which region of the country you are in.
Some states allow Middle School students who have show maturity, to attend night school. You can also attend night school if it required of you, say for example you are working for a greater family income during the day.

In general, a Middle Student would be likely to attend a High School to further increase their knowledge along with their generation.

Now, for a question you may have also asked is, Can you get into night school "while" you're in Middle School?

It all depends on your situation and requirements, but most likely no for the average Middle School student age ranges from 11-14.

I hope my answer has helped you in some way.

Thank You.