Can you play senior basketball even if you are in junior high?
No you cannot. This is because Senior is grade 12 which is high school. Junior high would not go up that high of a grade level.
Junior high and middle school are the same thing some people call it junior high and some people call it middle school. Since some people call high school senior high they call middle school junior high. This may be kind of confusing but middle school and junior high are the same thing just as senior high and high school are the same thing.