He has a point. If you want to discuss the importance of education, talking to a bunch of college graduates isn't going to fix anything. Do you think those college students are gonna say "Mrs Obama, how am I supposed to get an decent education when we barely have enough books in our class, don't have heat during the winter, and our teachers literally told us they're only here to get a paycheck?" That was my public school experience when I was a youngin. What she would need to do is take the conversation to the place that needs it most, and listen to the reason why the dropout rates are so high. If you watch documentaries like Waiting for Superman, you'll see it's not because kids want to be rappers and ball players. It's because a lot of the time we have shytty schools, creating shytty neighborhoods, which feed these kids straight to the pen.
It's like going to a church and preaching on the importance on believing in God. You're preaching to the choir.