Really depends on the quality/availability of design/tech teachers. My son has just taken his GCSE and it's expected to be his only fail. Despite promises and impressive presentations at GCSE selection time in year 9, the schools' promises have turned out worthless. In particular, they said nearly everything could be done by computer design and computer aided manufacture using routers, 3d printer, laser cutter, etc., so were trying to attract the kids who weren't actually that good with their hands (they explicity said that!).
In reality, the teacher he got was near retirement age and hadn't a clue about the CAD/CAM equipment (he was an ex Maths teacher who'd had a nervous breakdown so they lumped him into design/tech! for an easy life!). They spent year 10 making a wooden pencil case and a metal aluminium casting, no theory work at all, no sign of starting their project at all. Come start of year 11, he finally started talking about the project, then after 2/3 weeks he went off on long term sick. Cue a stream of supply teachers who weren't Design/tech teachers and just told them to do homework in lessons (baby sitters!). Finally, at Christmas, they got allocated a design/tech teacher, but he could only do one lesson per week due to timetabling. In January, they started the project planning, theory work, my son spent a few full weekends and many evenings doing the Computer design work etc and converting the data into the computer manufacture system (he basically taught himself how to do it). Then they finally started making it after February half term. Then the bombshell, it had to be completed by mid March, so basically just 4 weeks to make it, with a "proper" teacher for just 1 lesson per week. Then, even worse, because so many people were trying to use the laser cutter, 3d printer etc., his class were told they couldn't use any of it and everything had to be made by hand. So, basically, none of the class finished their projects.
Come the exam itself, general feeling from son and his friends was that they'd be lucky to get 25% of the marks as most of the questions hadn't been covered in class (they'd had no theory teaching at all).
So, before you go down the tech/design route, make sure that the school take it seriously and have proper teachers doing the lessons. It's clear some schools/teachers don't give it any importance.