I have a few thoughts.
Can you "glue together" a few different templates one based on a specific feature you need? Alternatively, have you looked at Bento? Might it have some options for you. Finally, I was in a very similar situation to you and found the missing manual book for FileMaker very helpful. Creating my own custom solution was a lot easier then I thought and fun to boot. If you go that route I would seggest you start with the feature you need the most and use a template for that. Then start building from there.
I've been looking for exactly the same thing for exactly the same reason! And, unfortunately got exactly the same results... I did find one solution but it seems to have been altered beyond recognition and packaged into a standalone (paid for) project. The other solutions I've come across are for running a whole school.
As MSpsi said, have you looked ay Bento? I started with that and have been happily using it since v1, but my needs have outgrown its abilities. I needed something more powerful for data analysis and Excel was not giving me the results I needed. I moved to FileMaker and the initial Bento work was easily imported.
However, I have found that if you try something then ask for help there are plenty of good folk on this forum who can give you pointers in the right direction - for example there is the thread I started asking for help with seating plans.
Perhaps we should invite all teachers using filemaker to get together in a forum of our own :)
Hm... I bought Bento right when it came out but I was very disappointed. Compared to FM, it's a toy.