BROOKLYN - The Department of Health is urging parents in Brooklyn and the rest of the city to make sure their children are vaccinated before classes begin.Officials say vaccinations aren't just a good way to protect against serious diseases; they're also required by law. For the first time, the Tdap vaccine is mandatory for all students who are at least 11 years old and entering the sixth grade. Students in day care, pre-school, kindergarten through fourth grade and sixth through eighth grade must also get the chickenpox vaccine.In addition, students in Brooklyn and the rest of the city must get their shots for the measles, mumps, Rubella, polio, and Hepatitis B. Vaccines that are recommended but not required are Rotavirus, meningitis, and the HPV vaccine for girls as young as 9 years old.Parents can either set up an appointment with their family pediatrician or children over 4 years old can visit one of the Health Department's walk-in immunization clinics.