Do I get a say in how many Ta's my son has?

Hi,

My Son is currently still on the old statement. He has severe SAL difficulties and needs  full time 1:1 support which covers breaks and lunch. For the past 2 years since starting primary school he has had the same two ta's split over the week, 1 doing 3 days and the other 2. I have now been told that in September he will have 3 ta's. 1 doing 3 days, the other 1 day and the other 1 day. This is because they are taking one of my sons ta's for a new child and she is being replaced by a ta with no experience. I feel this is going to cause alot of stress and confusion for him chopping and changing like this and also i don't know how they will communicate with each other or the class teacher with regards to his work. I think really the new ta will just be babysitting for the day each week.

My question is, can i say i don't agree with this and what rights do i have with regards to who my son has for teaching assistants?

Thanks.