We also live on the Slough/Bucks border, but in Bucks and my son goes to a grammar in Slough.
There are two types of forms. One type is to apply for the 11+, and the other type is to list all your school preferences (for any school grammar, non-grammar, in you local authority or not) to return to your ocal authority.
1. The form that lists all your school preferences. It is refered to sometimes as the 'common application form', or CAF.
You must only return ONE common application form. In your case, I am not sure to which of the two councils. Here's their details if you want to contact them.
http://www.buckscc.gov.uk/bcc/content/i ... =987793428
2. The form(s) to apply to the 11+
If your son goes to a Bucks primary, he will be entered by the school to the Bucks 11+. However, the school may or may not enter your son for Slough 11+. If they don't, you have to enter them separately. You will have to fill in another form giving your order of preference for the Slough grammars. May be it it this other form that you have with you now.
How to fill the forms
The application form for the Slough grammars:
Just list the grammar schools you are interested in order. You must have Langley or Herschel as first preference because they are over subscribed. You can have Slough in second place, but not in third place as you may not have a place.
The form for the council (Common application form):
you can have a mix of schools from both LEAs. The school order is very important.
The order for the Slough grammars must be the same as the order on the application form fot the 11+ in Slough, but you may have Bucks or other schools in between.
For example, if you have given for the slough 11+ the following order
You can have:
3. Another school - could be a seconadry
but you can't have
3. Another school
You also need to be aware that the place allocation is very different between the two authorities.
Bucks allocates places according to where you live (catchment ot distance to school). As you live in the catchment of Burnham Grammar, you will be offered a place there.
Slough grammars allocate places according to the 11+ score independently of where you live. So your son can also get a place in one of the Slough grammars.
You are in a good position, and can chose according to the school you prefer in term of grammar schools.
In term of secondaries, are you in the catchment of a Slough school or a Bucks school?
All the info that I have is from last year. So, just in case something has changed, double check with Bucks CC for Bucks, the grammar schools in Slough.
I could give you more details about all this, but it may get very confusing.
Please don't hesitate to ask more questions or if this is not clear. You will probably feel that you have grasped the ins and out of the 11+ once it's over. That's what happened to me last year.
Hope this helps