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.
i am a retired 'professional' (social work), and i know professionals in a variety of careers (information technology, law enforcement, architecture, engineering, law, speech therapy, entertainment, medicine, educators...) and for the most part NONE of us were required nor was there the expectation of doing volunteering. going to meetings-that was part of our jobs weather it fell within schedualed hours of standard work or not, symposiums, trainings-it's known as professional development and in some cases it is required to maintain professional lic.-so again 'part of my job'. many of us had opportunites to volunteer-we even had volunteer bureaus within our agencies that would faciliate opportunies for us to do so, and some did-but it was always with the mindset that it was TOTALY voluntary on our part-NOT AN EXPECTATION, NOT A REQUIREMENT. if it had been-IT WOULD'NT HAVE BEEN VOLUNTARY.
while i don't agree with the 'it's not in my contract' card being pulled to explain why a teacher (or a social worker or other professional service delivery persons) won't meet with someone or won't do something-in all honesty it often comes after years of unsuccessfully trying to explain to parents, students...that you have other items to attend to and being responded to with disbelief, disdain, sarcasm and in some cases outright hostility. saying 'it's in my contract' or 'it's department policy' takes the issues out of your hands-if the person wants to argue it further it refers them the admin.
one issue i can see with teachers or other professionals who have traditionaly done unpaid activities outside their actual 'contracts' is the issue of 'past practices' rearing it's head and working negativly for both the professional and the students/clients. if an employer can show that a person or profession has done a certain task or activity routinely (even if unpaid) over an extended period of time, it can be used to substantiate that task or activity as a part of the professional's base job duties. never mind that the professional has no training in it, and it was intialy done before greater demands were placed upon them. and although the activity is now taking valuable time from their core duties-it becomes part of doing their base job. this has been successfully used in some professions to substantiate elimination of other professionals who ARE trained and more appropriate to lead/guide/coach/train activities.
personaly i look at extracurricular activities as that-'extras'. nothing that i have the expectation are included in the base 'package' of my child's education. if a particular teacher wants to put in time outside the school day to sponsor one of these, it's not at the expense of short changing my child academicly in the classroom, AND THEY HAVE THE APPROPRIATE SKILLS/KNOWLEDGE for the subject-great. if they are, as was my experience in highschool-using instructional time to prepare for these activities ('students i'm busy today getting ready for this weekends such and such meet-just read ahead in the books, we'll catch up on what we miss next week

), requiring non participant students to use their instructional time to support these activities ('the drama club needs help constructing sets, so we're going to ignore the fact this is a humanities course that i teach and we're all going to go build sets for the next week'

), or spending so much time that they are disservising their day to day core duties ('sorry guys, i did'nt get those papers graded-late game last night', 'i know i was supposed to get together with you to help you with that math question you've got but i had to reschedual my x appt because the mathletes had a last minute cram session yesterday for the meet next week', 'guys, i'm gonna push back the unit i had you read for this week-i did'nt get a chance to put together the study guides

) then i want them to refocus on what their primary function is, work on that and remember (as my parents said to me as a kid inclined to want to do extracurriculars) 'extracurriculars come AFTER your work and family obligations'.
btw-unless a person has intimate knowledge of the consise existing and proposed contract language for an individual group of employees, i would suggest that they not jump to the conclusion that based on salary alone they are well paid. i worked for the highest paying public agency for my profession in the state of california. we had many people who commuted tremendous distances because they simply saw our salary as compared to theirs-they were in for a rude awakening when they saw that those higher salaries came with much reduced employer sponsored contributions to medical (and no coverage in many standard areas), low employer retirement contributions, provisions that require US to pay for mandated professional trainings, provisions that precluded us from taking part time employment that was the standard in our profession, and provisions that precluded us from volunteering in certain instances for certain agencies/groups we would have wanted to do. there are often trade-offs for a 'high salary' that more than offset it.