Newbe question. is it asterisk what I need?

Hello,

I am teacher. So I have certain relatively fixed hours where I do not want any stupid call get me on my mobile phone. On the other hand I do not want to be in flightmode all the time (there might be an important call).
So I look around for a solution on my (rooted) android that accept calls (depending on a timetable) and redirect them to a kind of vocal menu: the mobile device should pick up the call, and play an announcement that asks to decide to type (say) 1 for leaving a message and quit or to type 2 to really ring my phone (“urgent calls only”).

I believe asterisk to be able to do this for me, I seems available for android, but I would need some hint where to start searching.

Thanks a lot for your help, Eric