This might not be a very popular opinion, but if you are "teaching to the TAKS test," then you are teaching the curriculum that should be taught to the kids anyways. Now I will admit that if you ONLY do TAKS preps all the time, you are shorting your kids of higher-level thinking skills, but there are ways to teach TAKS-related topics and critical/creative thinking at the same time. I'm at a private school and I don't have to worry about TAKS, but we are required to teach the same TEKS that public schools teach so any child who leaves us for public school is prepared. TAKS is all about accountability, and accountability should be in place to make sure teachers are not doing a dis-service to our kids by not teaching them anything.
I don't know if and how your districts require you to use CSCOPE, but we use it strictly as a powerful resource. The main thing that it helps with is it actually defines what the TEKS are saying and what it is exactly you should be teaching. The assessments are also good. As far as the lessons, we have been told that it doesn't make sense to do CSCOPE lessons EVERY time you teach, but there are a lot of good lessons to expand on and to reinforce what you are teaching. If used properly, CSCOPE is a good tool. Whether or not it is worth the cost depends on the financial situation of your district.
Regarding certification, I honestly learned NOTHING through my education courses that prepared me for the real classroom. Teaching comes down to three things: passion for helping kids, knowledge for the subject, and accepting that kids today do not think like we do and teaching them how they learn best.