If you want DS to attend full-time or part-time, but more than he is, he can, unless the school is formally suspending DS. You do not have to accept the school unlawfully, informally excluding DS.
Until DS is compulsory school age, you can choose to send DS part-time if you want to, but it is your choice, not the school’s decision.
2.17 of the School Admissions Code (which you can see here) makes it clear it is the parents’ choice:
“Admission authorities must provide for the admission of all children in the September following their fourth birthday. The authority must make it clear in their arrangements that where they have offered a child a place at a school:
a) that child is entitled to a full-time place in the September following their fourth birthday;
b) the child’s parents can defer the date their child is admitted to the school until later in the school year but not beyond the point at which they reach compulsory school age and not beyond the beginning of the final term of the school year for which it was made; and
c) where the parents wish, children may attend part-time until later in the school year but not beyond the point at which they reach compulsory school age.”
You may also find the statutory school suspension and exclusion guidance helpful here. Most of it applies to those below compulsory school aged. Where it doesn’t, it explicitly says so as stated on page 6.
Some bits you particularly might find helpful are:
“19. Suspending a pupil for a short period of time, such as half a day, is permissible but the formal suspension process must still be followed. Each disciplinary suspension and permanent exclusion must be confirmed to the parents in writing with notice of the reasons for the suspension or permanent exclusion.”
Also of interest may be:
“20. Any exclusion of a pupil, even for short periods, must be formally recorded. It would also be unlawful to exclude a pupil simply because they have SEN or a disability that the school feels it is unable to meet…An informal or unofficial exclusion, such as sending a pupil home ‘to cool off’, is unlawful when it does not follow the formal school exclusion process and regardless of whether it occurs with the agreement of parents.”
And
“30. A part-time timetable should not be used to manage a pupil’s behaviour”
In addition to this, the LA is responsible for anything detailed, specified and quantified in F of the EHCP. Is there anything in there that isn’t being provided?