It is a shocking diagnosis, even if you expect it, and I'm not surprised it has taken a while to sink in.
In theory, the school shouldn't be resistant to apply for an EHCP unless they don't think they (yet) have enough evidence for the Local Authority (LA) to agree to one.
Schools generally like it when LAs grant an EHCP as it means they get more formal support/intervention from outside teams and that the school also receives funding specifically for the support the child needs.
The difficulty getting an EHCP tends to come from not being able to put together enough strong evidence and paperwork not only of the child's needs (diagnosis) but of the impact that has in school and also a record of what has already been done from within the school's existing budget.
Some schools may already know that their particular authority wont approve the request until e.g the child is older or there have been more professionals involved. And schools sometimes don't like applying if they think it will be turned down as it wastes time and also (they worry that...) it makes future applications less likely to be successful if they have a reputation for applying too much. Technically that last point shouldn't be true but I know many schools who feel it is.
Also, some LAs have some other procedures in place first. E.g. for under 5s some ask schools to apply for an Early Years fund to support the child for a few years until the extent of their needs and the impact on their education is clearer.
Other times the school might feel that the child's need isn't great enough for an EHCP...do you know if they have concerns about him or do they think he's alright in school?
Basically, if the school does appear resistant, it's worth trying to find out what they think the stumbling block is..... it might be something that you can help them overcome or it might be that they're right to need a few more terms of school-funded intervention and support.
