Newsflash: MOST professionals do this all the time. That is part of the deal when you are a professional. If you don't want to be considered a professional, then sure, don't do the extras BUT do call yourself what you are -- an hourly-wage, union employee. You cannot both claim professional status and behave like a factory worker clocking out at the end of the shift.
And FWIW, I don't think that any of this is about money -- the teachers in my school district are among the highest paid in the state in an area which does not have the highest cost of living (but which does have among the highest property tax rates in the state). And yet, these highly-paid teachers regularly tell parents that they can't meet after 3:14pm because, "It's not in the contract. " This was the same attitude in another school district where the teachers were not as well paid. So, it's not about the money, it's about the attitude -- the non-professional attitude of "I'm paid by the hour and the minute the bell rings, I'm outta here and screw you." I used to have a lot of respect for teachers, but no more, not after 9 years of dealing with this attitude in two different school districts.