I am certainly in favor of pre-testing to see what students know and can do. However, it may not be possible or it may not be the best use of time to bring every student up to the same level before moving on. We risk boring the best students who need to be challenged more. Diverse ability levels are hard to teach en mass, but easy to teach one-on-one.
Therefore: CREATE A COLLABORATIVE STUDIO CULTURE
I find it useful to tutor the advanced students on how to tutor the slower students when the needs arise? I like to challenge every student to help with the teaching and learning. If peers can learn to teach with questions and by helping to set up experiments, (not doing things for them) all will benefit. Self-instruction and peer-instruction are natural and often the most effective ways to learn. The culture of an art classroom should be a learning environment where citizenship means that we all pitch in to leave no mind behind. I call it creating a collaborative studio culture.
If a pre-test is used, try asking them to name the most famous woman artist they know. I have had many elementary education college students who could not name one.