It does look like there is an erroneous gap in your orders. However if the order is over 12 months then presumably the Resident Parent could go to the CMS and as they are under 20 and in full time "non-advanced" education then I would have presumed they are still in scope
www.gov.uk/what-different-qualification-...qualification-levels
assets.publishing.service.gov.uk/governm...to-tell-us-about.pdf
Full-time, non-advanced education and approved
training courses
Children over the age of 16 need to be in full-time ‘non-advanced’
education at a school or college, or starting an ‘approved’ training
course, to qualify for
child maintenance.
Full-time, ‘non-advanced’ education means that, on average,
the child spends more than 12 hours a week on tuition, exams,
practical work or supervised study towards certain qualifications.
These include but are not limited to:
• GCSEs
• A levels
• NVQ and SVQ level 1, 2 or 3
• BTEC National Diploma, National Certificate and First Diploma
• SCE higher grade or similar
Any qualifications above this level (for example, a degree) are
called ‘advanced’ education. If you are not sure whether your
child’s education counts, you can contact the Child Benefit Office
for more advice.
Approved training is various training programmes arranged by
the government.
For a training course to be approved it should be one of the
following:
England - Foundation Learning Programmes (previously known
as ‘Entry to Employment’) or Access to Apprenticeships.