Well at least for the LISD (Leander Independent School district) part of it. Found it in this article about the LISD budget.
Here are the Tax rates for the last 5 years.
2007: 1.333400
2006: 1.643800
2005: 1.750000
2004: 1.790000
2003: 1.830000
2002: 1.722000
That is the big drop, probably because of the large influx of people into the area that can enable them to increase the budget without increasing the tax rate because of all the new homes in the area.
