I really love how for Home Ed teens exam stress can be minimised. We can stagger their exams, so we have sat five GCSE's over six months with two last November, one in January and two in the last few weeks (May). So for each set of exams we have been able to spread the pressure and focus really intensely on each subject at a time. We have also found this good because it spreads the cost of paying privately for exams. Also your kids can take them at any age that suits them.
We have only aimed for five GCSE's for each son, as this is plenty to attain most goals, except perhaps very top fields of expertise like medicine or veterinary science. My eldest is now at a top University studying law and my youngest has several options open to him for September which he can choose from soon. Only doing five subjects really reduces the stress of exams, it also means your kids can pick the subjects they really want to do, except perhaps for Maths and English, which are a core requirement for many further education options, but not all so it's worth checking. GCSEs aren't the only exam option for Home ed, check this link for more information: http://he-exams.wikia.com/wiki/HE_Exams_Wiki
We have also combined exam pressure with fun activities when exams or revision are not mentioned, so this week we have been caving and rock climbing, being in the Peak District really has advantages. It may have been a small tactical error to do rock climbing on grit stone which makes your hands bleed, just before an English exam, but oh well, my son is tough. 😜
The other stress relief is needed for the HE parent, get a bunch of other HE Mum's around you who understand and you can vent to. This is a good Facebook group for this: https://www.facebook.com/groups/HELinksUK.IGCSE/
Exams aren't necessary for every child, but if they are something that suits your child's future plans make them as fun as you can as they can be quite dull, tedious and stressful.