1:1 TA expectations

As a former inclusion HLTA who helped new 1:1 TAs with planning and differentiation:

It's useful for the TA to have a look at the week's planning a little in advance (or, if that would be inconvenient for you, to give them an idea of the topics that are going to be covered). This gives them the opportunity to find or create adapted resources, visual prompts for the child, or whatever else is needed. It's hard to say anything specific because it depends very much on the age of the child, their particular needs and how far they're able to access the mainstream curriculum - I can give more detailed advice for EYFS or KS1, if it'd be helpful and you're able to share more information on the specifics.

If the school doesn't have a lot of shared SEN resources, the TA should be given a short amount of planning/prep time to get things ready.

The 1:1 TA should also have access to the child's files to see if there are any activities recommended by external agencies to be done in school - SAL target work, physiotherapy activities, etc. and have the opportunity to fit these in somewhere during the week. It sounds obvious, but I've been in schools where these are filed by the SENCO and not passed on, which is fine if the TA is experienced/pro-active and knows where to look, but that isn't always the case.

It really would depend upon the child. Some will just need a TA with them to keep them on track and remind them what they need to be doing and promoting them with questions. Others may nees to have the work chunked and down times included. While others will need their work delivered to them through a hidden curriculum where they think they are playing/ doing something they enjoy but are actually learning.
As to how much of this should be planned by the TA the answer is not a lot. The teacher should be planning a lesson and of any tweaks/ changes need to be made then a discussion should be taking place or separate planning provided