I formerly worked in a health department and gave vaccinations, so my info may not be 100% current.
I will speculate that your state recently mandated HBV vaccination and they are trying to "catch everyone up", which they do by mandating it for some year or years of entry into school. In my state, we started by making it an optional vaccine for infants and then we mandated in for 6th grade entry and kindergarten entry and then it gradually became a necessary vaccination for school attendance (unless your doctor releases you for medical reasons). So this weird pattern of vaccinating 4th and then K students seems like they are playing a little catch-up to get kids vaccianted.
Happily Hepatits B deaths are down significantly with vaccination. This is the truth and cdc site will reflect this. Hep B death is not a quick and easy death; it is chronic illness (that can be managed) with a risk for liver cancer and liver failure. I am a nurse and 300 health care workers per year died from Hep B at one time. Hep b is a bloodborne pathogen and is spread by direct contact with infected blood, sexual intercourse, needle sharing, etc. At one time, I had some (by now pretty old stats) that noted that risk of transmission with infected blood was 30% for HBV and something like 0.3% for HIV, so HBV is "easier" to get from a single exposure to infected blood.
The CDC's goal is to give children lifetime protection from a preventable disease that carriers considerable morbidity and mortality.
I think most parents wonder, why should I vaccinate my kid? At kindergarten, they aren't having sex, using needles etc. Surely actual risk for accidental transmission from an infected child in a playground accident with bleeding isn't too significant. To me, the main ADVANTAGE is that your child has protection from this bad disease at the moment he may practice risk behaviors. You don't have to say, "Gee, Susie, I'm worried about those friends you hang with; let's get your HBV series started." NONE of us plan that our children will engage in risk behaviors, but sometimes they do. (Including getting drunk and having sex with partners they wouldn't ordinarily choose.)
Finally, a friend of mine (a nurse) felt that the long term studies are not yet able to support that the vaccine given to an infant will give protection in young adulthood [probably because of the youth of the vaccine]. I have not read studies on this but my own hepatitis b vaccine is at least 15 years old and my titer (level of protection) is just great. Many experts feel that even a low titer does not necessarily mean that you won't have protection at exposure because of the marvelous workings of our immune system.
As pro-vaccine as I am, I am a little scandalized at how punctured our kids are between the routine baby shots, HBV, and chicken pox. It is good to ask questions. I would direct you to my favorite site for the Center for Disease Control. www.cdc.gov
I would guess that they have faq's site for Hepatitis B vaccination.