OP - as you seem a bit hazy on double v triple science GCSE.
Double Science - 2 GCSEs (Core and Additional)
6 papers & 2 practicals:
Physics1, Chemistry1, Biology1, practical coursework (core)
and Physics2, chemistry2, Biology2, practical coursework (Additional)
Triple Science 3 GCSEs (Either Core, Additional, Further, OR more likely Physics, Chemistry, Biology)
9 papers and 3 practicals: what you had for the double plus paper3s in each science and another practical coursework.
So double science gets you to about 2/3rds the level in each science that triple would.
Is triple taking an extra Option block compared with double, or is it 'accelerated' ? (if accelerated may be easier to drop down a set than if it is a whole option). There is a lot of content in Double, and at DD's school the accelerated goes very fast and some self teaching is needed. I think they may have even now dropped the accelerated option.
If he might want to do any science A levels then worth persevering with triple, otherwise double is OK. Physics 2 gets quite mathsy, so I would expect Physics3 to get even more so.
Speaking as someone with Physics A level, I think double is quite sufficient for a solid background in science for everyday life.
Last science GCSE exam will be around 19th June or earlier so tutors busy with y11 will become free then.
You do have the appropriate science revision guides for his board, don't you?