Now what can I do?

When looking at plans A, B, and C (hypothetically), they are all going to be high, especially if your "baby" is cursed with being a boy (like myself). With that being said, the best thing you can do is list them under YOUR policy, and even list yourself as the primary driver for their vehicle, and put them on a cheaper car (if applicable). Some insurance companies allow this, other's do not, you'll just have to call and ask your agent.

Also, there are some steps that your kids can take to try and keep the prices to "reasonable" levels. It is strongly encouraged that your kids do well in high-school and college, and if they retain a greater-than 3.0 GPA. This is very doable, as it is only a B average. Another idea you can look into is raising your deductible to an obscene level and just hope your child doesn't get into a wreck, altercation, ticket, etc, as that will be a VERY high price to pay. It is a gamble, don't get me wrong, but it may be worth it in the end. And the last suggestion for the night is to be sure to get insurance in which your house, and any other vehicles and items are insured on. Most companies will give you a worthwhile discount for insuring multiple items on one policy.