We've been really lucky with DS. We had no issues in the council agreeing to the EHCP, and other than minor disagreements with the council's case worker about my amendments, we got through panel OK.
I went to the secondary school and we had a tour with the deputy SENDCo to find out what provisions the school had which DS would benefit from. I then worked with the SENDCo and amended the draft to include those provisions. This meant that they were able to say they could meet his needs and were named on the EHCP.
He started there in Sept and they've been amazing. They've put everything in place (1:1 TA to assist with communication, plus a pass for early leave, access to a break out room, access to toilets and queue jumping in the canteen and a laptop for longer pieces of work) and are really supportive. He had 100% attendance for the first half term, which is amazing, as EBSA was a massive issue in primary where they didn't really get to grip with his needs.
He's very academically able, but just needs a bit of extra support for communication and his anxiety re crowds.
I think it very much depends on both the child's needs and the school's ability / willingness to assist as to how successful the EHCP can be.