Formative vs. Summative Assessments

Over the last few months, many of us have been attempting to prepare our juniors for the upcoming ACT test. The big summative assessment, that according to some of my students, will determine their future. Ok, in my mind some of them are putting a little too much pressure on themselves when it comes to this test. Yes, it is a big deal, but are we putting too much into the whole idea? What happened to addressing what students know? What about all of these formative assessments that we are completing to determine if students are really understanding content? My concerns have increased since my students began commenting on the practice tests that they took in order to prepare for the ACT. Numerous students have voiced concerns that they have never of some the things found in those sample questions. Some of them have also complained that they have no idea what the charts and graphs mean or how to even read them. So, I am then forced to look at my teaching skills. Am I the one that is dropping the ball and not teaching my students the skills they need to take these types of tests? Is it too late to teach these skills by the time they get to me as juniors? Do I place blame on those teachers that came before me in the educational careers of my students? Or, maybe we lay blame on the test and those that created it. Many of my colleagues have argued that we should forget everything else and just "teach to the test". I'm not sure this is the answer either. Although, I'm not sure that there is a concrete answer out there. Anyone else have any ideas?