Student car insurance can be expensive for several reasons.
Firstly the driver is likely to be under 25 and policies are always more expensive for young drivers. The car is likely to be parked on a road or driveway at night and so this will make it more expensive than if it was parked in a garage. The driver is likely to cover long distances at term end and beginning times as they will be likely to drive to their parents home which could be a long way away from where they are at university.
There are companies which offer specific student cover and this could be worth investigating but could be dearer. Doing a price comparison is always a good idea as it could save money. There also may be some cash back offers or discount vouchers that you could find on line to help reduce the cost. It may even be worth considering managing without a car until you are over 25 as the costs then will be lower.
As a student try to be careful where you park and do not leave valuable possessions in your car. If the car gets broken in to and you have to make a claim then this will increase your premium even more. Do your best to drive safely so that you do not have accidents and this will also prevent your premium from going up. You will also be able to start building up a no claims bonus which could make quite a difference to the cost of your premium. It could be worth calculating whether a protected no claims could be worthwhile as it is more expensive but may help to prevent increases in premiums if you have an accident in the future. If where you park is unsafe then this could be an option worth considering.