Yes, of course immunizations should be mandatory. Me vaccinating my child protects your child from disease and vice vera. There will always be a small portion of the population that cannot be vaccinated (due to allergies or compromised immune systems); vaccinating everyone else protects them too by keeping the disease at bay. Vaccinations are one of, if not THE, greatest technological advances of our era, and we are STUPID not to take advantage of them.
Immunizations for public school children should be mandatory because it prevents the spread of diseases that have been largely wiped out in the developed world. Healthy kids stay in school and learn better. Immunizations foster a good learning environment because everyone isn't getting sick with diseases that have almost been eradicated by modern science.
This idea, while good in theory discounts the fact that immunizations do not work equally for everyone and also may not protect as long as they are supposed they do. Some vaccines are given to protect in the slight possibility the child may be exposed, for example Hep B- a sexually transmitted disease - is a vaccine given to infants! The effectiveness of this vaccine is only 10 years! This vaccine would be better given to teens or young adults who would benefit from its protection, not infants who will likely not benefit from having it. Too many policies have been made based on how much many can be made. Who profits from these decisions? Protect who needs to be protected don't waste money better used elsewhere.