I am so sorry to hear about your dad. It must have been a huge shock to get such devastating news that your dad is likely to die from his cancer. It is not surprising that you are feeling overwhelmed by it all and stormed out of lesson at school.
When you are dealing with things as hard as this, it really is impossible to hold it all in, as you apparently have tried to do at school. You need to be able to talk to someone about what's happening and how you feel about it. If you don't vent your emotions but bottle it all up inside you, then it will come out in some way or another and maybe at times when you feel the circumstances are not the best for you. You mustn't feel embarrassed though, about storming out of the lesson as it's a perfectly normal way to react when you're under the amount of stress that you are now. However, it would be better for you if you could talk about your emotions before they build up too much inside you so that you can get the support you need to deal with things bit by bit. When that's said, sometimes things really are so difficult that we can't control how, where or when we react with emotional outbursts. If that happens again, try not to escape from it on your own, but try and find someone that you can talk to and who can support you there and then, whether it's a good friend or maybe a teacher.
The best thing is, don't try and hold everything inside you - talk about it and hopefully you'll get support from your family and other people around you who will help you through this.
Remember, you can also talk to others in the riprap forum who maybe more than others can understand what you're going through at the moment. Remember, you can also get in touch with us anytime and we can talk things through with you.