This number calls constantly with some bs automated message

This number keeps calling my cell phone at the same time on Thursdays and Fridays.It will try to call at 7:15 pm CST and if I don't pick up it will try again at 7:28 pm CST.I don't pick up because it costs minutes,and they don't leave a message,but I did a search and the number is registered to Gateway Middle School in St. Louis,MO. I have a kid in middle school,but we live no where near St. Louis. I don't understand why they would call.

Just got a call from this number and when I answered a male voice on the other end said, "Momma?"  
I said, "excuse me?" and they hung up.
MK mentioned that it is from Gateway Middle School in St. Louis, MO ... so I am assuming it was a middle school boy that dialed the wrong number.