This question asks for opinion... In my opinion Hansberry's play is not appropriate for students in 7th grade. This is not true because the material is "sensitive" or "mature", but because some emotional maturity is needed to understand the play.
The conflicts between Mama and her two children are highly important to the meaning of the play and are probably too nuanced to be fully understood by 7th grade students.
Ruth decision about what to do about her pregnancy is presented in the play with enough subtlety that an average 7th grade student may not understand the situation.
This is not a play where everything takes place on the surface and in the open. Innuendo, subtlety, and nuance are some of the most powerful aspects of the play and are also the elements most likely not to be appreciated by a 7th grade class.
With this said, there seems to be little in the play that would shock or disturb a young audience.