There are many children that don't fit into School for any number of reasons. Some are School refusers, some cope by taking large amounts of time off School, some go through attending School but suffer in other ways.
My youngest son was deeply unhappy at School, and although I tried for some years to put things right, I finally came to the conclusion that if a child is traumatised and unhappy at School for whatever reason, then at the end of the day all of their energies are going to be taken up with their anxieties and fears and that of course that leaves very little of themselves left open to learning - the whole purpose of being at School!
Is your Dad open to the possibility of Home Education? Is the cost the only thing that is putting him off? There are many different ways to Home Educate and it can really be as cheap or as expensive as you want it to be. Here are some links and examples that you might find helpful.
Some online Schools in the UK are:
http://www.firstcollege.co.uk/
http://www.briteschool.co.uk/
These are live virtual classes where you do your work at the pc with a group of other kids in the same virtual class. This is probably the most expensive option with fees of typically £2,500 a year for your year group.
There are also Companies providing curriculum packs for School year groups and IGCSE if that is the way you want to go, have a look at this website here:
http://www.structuredhomelearning.com
http://www.oxfordhomeschooling.co.uk/
One of my sons came out of School in Year 8 and the other in Year 5 and have really enjoyed learning at home, it's given them much more freedom and time to take on other interests as the amount of time they have needed to spend on their learning at home has been far less than at School. My son that came out in Year 8 went on to take all his GCSE's and A Levels at home and has had time to start his own business. Your Parents don't need to be Teachers at all - (I'm not)
Other Home Education websites that might be of use are:
http://www.education-otherwise.org/
http://www.thenuk.com/
http://www.home-education.org.uk/
http://home-ed.info/
There are other alternatives to online schooling, and personally we never took that route ourselves.
With GCSE's there are correspondence courses available through NEC, ICS and Oxford Home Learning. These courses have Tutors that mark your work as you go through the course.This way of learning didn't suit us, but it does suit some people. NEC and ICS courses can be bought with Tesco Club-card vouchers if you collect those at all.
There are a number of Home Education groups all doted around the Country and have small learning groups where they share Tutors and the cost of this can be around £5 an hour. There are a number of these where I live and in most GCSE subjects and KS3 courses too. To find your local Home Education Group and see what they have to offer look here:
http://www.education-otherwise.org/local…
Some Home Education Groups (depending on where you are in the Country) have arrangements where children can attend College or Adult Education Classes too for free.
Our learning has been relatively cheap, we use the internet a lot, there are some great websites available (google 'KS4 online' or KS4 or GCSE online resources') and a host of websites will come up in just about every subject. There are second hand text books available on Ebay and Amazon and we use the shared Tutors for a couple of subjects (not all). If you want to follow the National Curriculum or GCSE's this information can be downloaded free online. The AQA website has a syllabus of all the subjects you need to learn for GCSE's ( so it is easy to buy the right books) and also past exam papers to practice with.
A great (But not free) resource for Maths is Conquermaths, where each maths lesson is broken down by a tutor in easy to explain steps. There is a discount for home educators.
The benefit of working from home is that you will not need as much time with your subjects as you do in School and many Home Educated children take their GCSE's early but take their subjects over 2/3 years. You will need to pay to take your GCSEs. - more here:
http://home-ed.info/gcse.htm