Today is the first day of classes for some 100,000 Jefferson County Public Schools students.More than 60,000 of them will be riding a bus. Motorists are urged to use extra caution and be prepared for more frequent stops as buses pick up and discharge students.JCPS officials say bus ride times for youngsters may be a bit longer than usual for the first two weeks or so, as drivers get accustomed to new and adjusted routes.Many Catholic schools in the area will begin classes Wednesday.