As you'll hear, teacher rewards hits for six (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Homophones (as you’ll hear) of SIR (a male teacher) + PRIZES (rewards). Hit for six (as a verb) = slang for greatly surprise [someone] by doing something unexpected. (From the cricket term for striking the ball out of the playing field.)