You the sit exam in Sept and get result before you apply for a school place. This is so you can look at the results and only then, on the basis of those results, do you assess which school to apply to. So even if you sit the exam at what you thought was your first choice, you may decide after you get your result, to alter which schools/ order of schools to apply for; you could even decide not to apply for a place at the school that you sat the exam; the choice is up to you.
Therefore, you can sit the exam at any of the CSSE schools, bearing in mind that if its a single sex school then it will only allow children of that gender to sit the exam at that school (eg boys at boys schools such as KEGGS). Chelmsford girls is now offering a different exam, which will be held on a different day, so girls from the chelmsford area will now have to travel to Colchester or one of the Southend schools to sit the CSSE exam.
The large schools (such as KEGGS, Colchester, Westcliff and Southend High schools) are very
busy, and could intimidate a nervous child.
My DDs sat at Chelmford; there were a lot of parents/ children, parking was dreadful and some of the girls were upset during the exams. Although parking for Chelmsford schools should be better this year as KEGGS and CCHS will be holding exams on different days, I would still advise people to get there in plenty of time to allow for parking.
You could consider the schools that offer only a few places as these tend to have fewer children sitting the exam. ( Such as Shoeburyness High School or Cecil Jones.) As fewer children sit the exam here, it is a quieter experience outside the exam halls.
The exam paper is the same at all schools and all modulators try to ensure that exam rooms are quiet. If a child at any center becomes too upset during an exam, the modulators will remove the child to stop them disturbing others.
One consideration is distance to travel, personally I feel that you don't want a really long journey prior to the exam, so I would opt for the closest test center.