I am but up in Scotland so it might be a bit different. I find we get mixed advice from different people e.g. members of SMT and the LA Early Years Team. E.g. we shouldn't do gathering time vs. they should sit through (boring) assemblies.
We have a v. small peg area so flexible drop off/pick up times are necessary to avoid overcrowding. So they can play freely (but only inside) for the first 15 mins. Then we gather in groups for gathering time. This is about 10-15 mins with register and an active participation activity around sounds or numbers or on our topic. This is when we do child-led planning too.
Then they can play freely inside and out. We have four zones each staffed by a teacher/nursery nurse (we are a 2 class nursery). The zones are child led but may have an adult-led activity for the children to opt into. Our zones are Outside, Expressive Arts, Role Play & Small World and Snack.
During this time we might go out e.g. for a walk, to the school library or to do gym or music and movement but this would only be about half an hour at most so still plenty of time for free play.
We have 4 aspects of the curriculum to focus our observations and assessments on each term plus a literacy and numeracy outcome each week. We've only just started doing this but it seems to help focus our observations.
Towards the end of session we tidy up, brush teeth and then have another gathering time until/while parents pick up. During this time I usually do songs and stories with counting songs and nursery rhymes and discussion around aspects of reading e.g. parts of a book, types of books, discussion re prediction, sharing (and for some justifying) opinions etc.
I personally do not like specific assessment activities (the other teacher disagrees with me on this) as I believe it is better to have an area of assessment e.g. counting skills and look for different opportunities for children to demonstrate this. It might be that a child appears not to be able to do the activity you've chosen because it's not of interest to them or they really want to go and paint a picture so rush or stop counting at 3! Instead I would approach the child I was wanting to assess when they're engaged in an activity e.g. building a tower "wow that's tall! How many bricks have you got there." or they're watching cars go past outside "how many cars can you see?"