Dev Bootcamp gives out our own custom prep material about a month before a cohort starts. You're interacting with other students and staff online starting then. Our prep material covers everything from the basics of programming up to simple object-oriented programming.
Some students will be farther ahead, but one thing we make clear to students on day 1 is that they're as responsible for creating the learning environment as we are. In fact, they outnumber us, so in many ways they're more responsible. :)
We emphasize patience and empathy, so students who are behind get mentorship from the students who are ahead. It reinforces the learning for the more advanced students and shores up the less advanced students.
Starting Jan. 28th, we're moving to rolling cohorts, where ~15 students enter every 3 weeks for a 9-week program. This way there will be a "senior third" expected to mentor students in the "freshman third." You'd be able to seek out that struggling student and give him the help they needed right when they entered the program.
Also, Dave, who is a badass at every level, joined the DBC team last month. I love that man and his squirrel-as-a-running-back t-shirt.