Not sure how it will work, lots of 16 year olds are still in Y11 or otherwise will start 6th form or other compulsory education.
DD was given NCS details at the end of Y11 but she found it very uninspiring and hardly adventurous.
While it is applaudeble to promote volunteering, my DD's 6th form is asking for 30 hours per week school work commitment. That's basically a full work week if you add 2 hours per day commute for her. And I am sure there is more to come when they prepare for mocks/exams.
She is an Explorer Scout and also volunteers with the Beavers since 2 years now. She loves it and it is good for her but she did pause it during exam times.