[Dustoff45]

I'm thinking that's a security measure

Yes USSS often will line up trucks to block the downrange view of potential snipers. But school buses with all those windows, not so much.

[SamAdams76]

Yes USSS often will line up trucks to block the downrange view of potential snipers. But school buses with all those windows, not so much. Correct me if I'm wrong but I'm thinking passing through two sets of windows would be enough to deflect bullets from their desired target at long range.