A city school bus side swiped my car. Do I have the right to sue for full damages?

Unfortunately, the person you spoke with is right, although for different reasons than immunity.  In fact, the city ( a political subdivision in legal talk) is liable for damage arising from the operation or use of a motor vehicle by its employees.  However, the political subdivision is entitled to a set off (credit) for any insurance benefits that you receive or are entitled to receive.  In your case, you have comprehensive collision coverage under your automobile insurance to cover your damages, less your deductible.  Therefore, the city is entitled to a credit for the amount paid by your insurance company for your damages.  In other words, the city only has to pay your out of pocket expenses after insurance pays, whether or not you formally make a claim under your insurance.  Since your only out of pocket expense should be your deductible if you make a claim under your insurance, then that is all you are entitled to from the city.  Even if you dont make an insurance claim under your automobile insurance, the city gets a credit for what it would have paid had you formally made a claim. Not saying that its right or fair, but that is what the law is. Good luck to you.