I invite you too to check out the city data forum... Lots of good threads about Katy too and a very active & helpful forum.
I cannot think of schools to avoid. People will pick and parse based on test score points or reduced lunch, but I don't take stock in that. North of I-10 is less expensive than the south side... So that may mean SOuth is "better"
We live in Cinco Ranch and I don't see how to go wrong here. Homes are 20 yrs old up to new builds. We all share in lots of parks, community activities and access to 8 pools.
The city of Katy is great for a small town real community feel (inside city limits zip 77493). One thing that I do lament about living in the new part of Cinco is the lack of roots, tradition, and community. Most are newcomers, which makes it easy to fit in at school, because there are always new kids! But many families work in petrochem and move a lot. We have lived here 5 years and have said many goodbyes.
Also regarding schools, Katy is still growing. This means building new schools and rezoning to fill them. For some people this causes a lot of angst too, although my family has been through an elem rezone & jr hi rezone without issue. Just don't buy a home based on a school you want to attend in 5 years, because the lines may change by then.
You mentioned your children will be attending a specialty school in West Houston. My best friend works at the Monarch School and another friend has a son that attends the Village School. If this is case of special needs, I would consider a neighborhood like Green Trails, or Nottingham Country Elem area. The commute to West Houston is less. Beautiful GREEN neighborhoods, and older schools mean they aren't dealing with overcrowding and starting everything from scratch
Hope that helps some. Hope to see you at city data too!