Colorado Department of Education Parents Page: under the 'Links' section click on 'School Accountability Reports' at that page choose the school district and then you can look at each school's report independently.
To access D20's website directly go to: http://www.asd20.org/education/district/district.php?sectionid=1
To access D38's website directly go to: http://www.lewispalmer.org/
Best of luck,
Its difficult to say across entire districts which schools are better or worse. By reputation, D20 has always rank high. However, in any district there will be bad/good/better/best schools comparatively. CSAP (state testing) results should be available online, by school and by district. There are more and more charter schools opening up but while some have very good reputations, others seem to have worse reputations.
Houses in D20 usually advertise "D20 schools" as a plus. My kids are in D49, and their school is newly certified as an IB School.
Hope that helps!