some schools dont screen. you can fill out and complete secondaries before amcas even verifies you by going to the website and d/ling the forms.
ie. columbia, hopkins, AE, etc...
other schools just send you secondaries without AMCAS verification, but they will not review your completed secondary until your AMCAS is verified. even before verification, they know via AMCAS that you are intending to apply to their school and will send out secondaries.
other schools that screen like the UCs will not send out secondaries until everything is verified at AMCAS and will send you an email emphasizing this.