Re: Positive negativity
I really hope that you are joking and are being flippant in your post, but I fear not.
The world is unfortunately a harsh place, but the last place that children should be receiving unwarranted harshness from is from their (supposedly loving) parents, if you genuinely want them to be able to achieve all that they can in life.
Yes, children need encouragement (and support) to study to the best of their abilities (or to find out what vocational talents they have which can be nurtured, if they are not so academically-minded, something often neglected, particularly in the UK (I don't know where in the world you are)), but they also need rewards, even if only token ones or just a show of emotional positivity, when they do achieve well or when they are showing signs of growing up as the good and well-rounded people that you hopefully want them to be.
Yes, children also need to be disciplined and taught correct behaviour (in appropriate ways), and I'm not saying that child-rearing is easy, but unfortunately it sounds from your post that you have a terribly authoritarian style of parenting, which will, I fear, if it has not already, kill your children's love for yourself, crush their self--esteem, and then make it even harder for them to be able to achieve their full potential in an atmosphere of harshness and negativity.
If "not getting a clip round the ear" is the sole emotional or other "reward" that you will be gifting your children for their exam results, you are causing unspeakable damage to your children (and their future hopes of stable jobs and relationships) and will be missing out on so so much of what family relationships are supposed to be about.
If I have misinterpreted your post, I very sincerely apologise, but if not, please ask friends, family, your doctor, etc for additional parenting advice if you (and your partner) feel that you are having more difficulties than you expect in bringing up your children. It is not easy and it is not something that we already know intrinsically ourselves, and risk getting it wrong (our own parents may not have always been the best examples). There is a saying "it takes a village to raise a child" for good reason. I wish you and your family well.