The answer is "Yes, in certain circumstances," but there was a procedure to go through.
Your case goes back several years. The pre-2007 CoP stated:
4.15 LEAs and school governing bodies must publish information about their
admission arrangements in accordance with Regulations. LEAs are under a
specific duty to publish information about admission arrangements for all the
maintained mainstream schools in their area .....
Variation to determined admission arrangements
4.19 Once admission arrangements have been determined, they can only be varied
in accordance with section 89 of the 1998 Act and the Regulations made under
4.20 Where an admission authority considers that the arrangements should be
varied because of a major change in circumstances, that authority must refer the
proposed variations to the Adjudicator, notifying all the bodies which were or
should have been consulted before the arrangements were determined. A major
change of circumstances is considered to be a serious and unexpected event
affecting the provision of education at the school. An example might be a fire that
has destroyed classroom space. However, a request to the Adjudicator for a
variation is not always necessary; for example, where a misprint occurred in the
published admission arrangements. In addition, an admission authority may vary
its admission number, irrespective of whether such a variation constitutes a major
change, where such a variation is necessary to implement proposals published
under section 28 of the 1998 Act. Where such a proposed variation is approved by
either the School Organisation Committee, without modification, or the Adjudicator
under Schedule 6 of that Act, an admission authority is not required to refer the
variation to the Adjudicator under section 89(5). However, where the School
Organisation Committee has modified the admission number, which forms part of
the proposals, the variation must be referred to the Adjudicator under section 89(5).
4.21 Admission authorities should consider very carefully before referring a variation
to the Adjudicator and should not do so once parents have been asked to make
their decisions, unless a major change in circumstances makes this unavoidable.