First off massive well done on going walking distance from your home and the supermarket shopping. I am currently at the stage of walking distance and can only hope that shortly I too can get to the supermarket. I think it's really important to see where you came from to where you are now. Could you perhaps think of smaller steps to get to the parent teacher interviews? As in maybe when you're at the school ask one of the teachers a quick question about the next holiday, or if they have anything due for the following day?
This could work as exposure I think, and please mods correct me if I am wrong. That would then gradually build you up from not going to the meeting to saying Hello to the teacher, asking a question etc. Or even see if you can attend a school day where they are holding a concert or something. Get the feeling of the school around you. Build from that and then the parent teacher interviews might actually become enjoyable?
In a different way of saying it if you want to swim then you do need to go into the water, but with exposure you don't need to jump right into the deep end...it's okay to walk slowly up to it.