[. You have nothing to lose by putting Tiffin first (if this is your preferred school) on your CAF.
Your only risk is that if you don't list Tiffin as your first choice and are offered a place at another school which you list as no. 1, your DS will miss out on his Tiffin chance even if he achieves a high score in stage 2. This is simply because if you get a place in your higher preference school, you are no longer considered for lower preference schools.
But don't forget if you live outside the priority area , no matter how good the score is you are very unlikely to get a place.
kashifzs - yes, Tiffin is a very popular school, their Priority Area (i.e. catchment) is 14km radius from the school and they offer places to in-catchment boys first, even if their scores are lower than those achieved by children who are out of catchment. I don't know which part of London you're in, so bear with me if what I say is not relevant to your situation.
I vaguely remember seeing something previously on their website saying that they get 10 applications per place and therefore it's unlikely an out-of-catchment boy would be offered a place, but I can't see that anymore.
In any case, their admissions policy indicates that applications from out-of-catchment boys are considered, so even if you didn't live in the Priority Area, I would still put it on the CAF as my first choice if I really wanted it. The worst thing that can happen is that they will not offer you a place, but it will have no bearing on your chances of being offered a place in your lower-ranked schools. Make sure, though, your think carefully about what school you list as no. 2 on your CAF, as that will become your top-ranked school if Tiffin does not offer you a place.
This is from the school's website:
Tiffin School’s Selection Criteria
10.1 Places will be allocated as follows:
i) To a boy who has an EHCP (formerly a Statement of Special Educational Needs) which names Tiffin School specifically on the Statement (...);
Places will then be allocated on the basis of selection by ability as demonstrated in Tiffin School’s test procedure in rank order of the Combined Mark within the appropriate category listed below and in the following order:
ii) Boys whose permanent place of residence (see Appendix B) is within the Priority
Area (see 11.1) of Tiffin School; and then
iii) Boys whose permanent place of residence is outside the Priority Area of Tiffin School (see 11.1).
11.1 All applicants who live less than 14km from Tiffin School, measured as a straight line, live in the Priority Area.
Their full admissions policy can be found there: http://www.tiffinschool.co.uk/_docs/adm ... 202016.pdf
I hope it goes well for you.