You cannot make parents or teachers attend meetings. It is as simple as that. To think that just because parents don't attend meetings that they aren't a part of their childs education is, well, silly. I am a disabled parent who spends a minimum of 6 to 8 hours a day (and help by grading papers at home in my 'spare' time...lol...) at my child's school, volunteering all over the place. My son is in a 4th grade accelerated class, but I spend most of my time either in the 1st grade tutoring and reading, in the office, or helping our PTO. The night that the current PTO board has their meetings is not an option for me. Doesn't mean I don't care, just means I can't attend a meeting on a Thursday evening.
There are other ways to bring parents who could attend but don't. Door prizes are very popular. Most local merchants will donate small items (sometimes not so small...lol...) on a regular basis. Floral items, oil changes, grocery gift certificates, jewelry, dash board covers, music gift certificates, dry cleaning certificates, etc. Nearby attractions, like theme parks, are also pretty good about giving door prizes. Then advertise the hell out of your meetings! Add babysitting services. Coffee and cookies. Anything and everything!
Remember that there are other reasons someone might not attend meetings, like cliques for instance. Even dislike of a board member will keep folks away. A new baby. A disability. Shyness. You never know what is going on inside a person's mind, or what their life is like, and you shouldn't pretend to or penalize others when you don't know their story. Or even if you do.
It is easy to want others to be as involved as you are, but I doubt that it will ever happen. I don't know of any parents in my area who can put in the hours that I do. Nor should they. If they are home helping with their child's homework, send cookies on party days, show up for awards assemblies, work full time, cook and clean, take kids to sports, karate, dance, or whatever, keep the baby's diaper dry, laundry, etc., they probably are doing the best they can.
Lighten up and appreciate those who do come and appreciate those who help out in other ways. Look at it like this: Going to church every Sunday morning of your life will not get you a ticket to heaven. Going to every monthly PTO meeting doesn't necessarily mean you are a good volunteer. Know what I mean?
Good Luck!