There's a couple of points that I really wanted to comment on:
I think it's silly to try to compare your salary and conditions as a teacher with what you would/might have been doing in "the private sector". The private sector is massive and complex and employs vast numbers of people in an enormous number of capacities. Assuming that you wouldn't have been a teacher, what would you have been doing? There are people out there with the same qualifications as teachers who are earning considerably less, and some earning considerably more. How can there possibly be a meaningful comparison? I think the public sector fosters this perception because it has quite rigid pay structures, making comparisons easy across sectors and professions, but you can't apply the same comparison to the private sector.
Having said that, there was recently a report from the Policy Exchange which compared people with the same job qualificaitons and experience across the public and private sector and found that public sector workers earned at least 2 per cent more.
The private sector simply doesn't offer employer pension provision to anyone under 35. There are a few rare exceptions, but, in all my working life - across large corporations, small businesses and charities - I've only had access to contributory, defined contributions schemes, with a minimal input from my employer which tended to depend upon how much contribution I was making.
Currently, with all the childcare costs I have to meet (which will double next year......) I'm making next to no contributions at all and my employer makes none. Once my children are older I plan to boost my contributions by as much as I can. One advantage of having a personal scheme is that I can choose how much to contribute at any time in my life. From what I've read, it seems that public sector contributions are mandatory - which must make things a lot more difficult. Having said that, if the benefits are contractual, then they have to be paid for. I think you'd be better off campaigning for a more flexible system - a variety of pension schemes that you can choose from, depending on how much control you want over the level of your contributions.
Finally - yes public sector workers are also taxpayers, but those taxes are paid for out of public funds - you're still a net cost to the public purse, where private sector workers are net contributors.