Is This Recognised?

The short answer is, yes!

In many U.S. states, homeschooling parents or umbrella schools can issue a diploma if the student has met the graduation requirements. A parent-issued diploma is legally valid in the States and widely accepted particularly when supported by transcripts, SAT/ACT/AP exam scores and/or a portfolio. 

However, I strongly recommend that home educators in the UK use an umbrella school for at least the senior (last) year - backdating to cover the whole time frame - so that the diploma and transcript can be issued by them; it then can be externally verified and easily recognised by UK workplace and educational groups. 

Following that, I then apply for a Statement of Comparability from ENIC to show a minimum of GCSE equivalency in Maths and English.  While not intensively covering all the work completed during high school, this document is particularly important. It translates the HSD into British terms and levels which then makes it easier for colleges etc to understand and accept.

Back-story...

I hit a roadblock when I submitted my first transcript and diploma to ENIC for a Statement of Comparability. I was working on the assumption that parent-issued diplomas would be accepted. (Parent-issued diplomas are common and accepted for homeschooled students in the US.)

ENIC confirmed that they would only accept accredited diplomas issued in America and refused my documents. After a fairly big panic, I then submitted the same high school records to Home Life Academy, an umbrella school in the States, enrolling her as a senior along with my second senior student. After three month's enrolment, both were issued with their official diploma and transcript which were subsequently awarded Statements of Comparability by ENIC.

Without this document, my students were going to be required to complete Functional Skills/GCSE English & Maths under the terms of the apprenticeships they went on to do. They were waived these requirements as soon as the ENIC documents came through. 

I know some parents have not needed the Comparability documents when for their child's college entry, but having it will open doors to a wider numbers of UK sixth-forms, employers and universities.