Sixth form application - first or second round?

[circular]

One of the sixth forms DD1 is applying for has 2 rounds of applications for external students.
First round for early offers, followed by internal applications, then second round external about 3 weeks later.

On the basis that she has predicted grades and other stuff in time for the early round, what are the advantages/disadvantages for applying for the first or second round?

I guess if she has good predicted grades now as it stands then go for the early round.

If she has mocks etc or a new report is expected soon then any new results will need to be used (and may be lower) for a later application?

or the opposite if expecting mediocre predicted grades might improve.

She should have all predicted grades etc in time for the first round, with little chance of improvement in between.

What we are really trying to find out is how it works - whether the first round just give out offers to the very top grades and bin the rest. Or if they get bunched in with the second lot of applications anyway. I'm guessing there will be a very limited number of early offers, as their internal students are guaranteed places on minimum grade requirements.

Very competitive comp - high 100's of applications for < 50 places. But they claim to look at the 'whole application' so it is not based on grades alone.

This is the only school we have so far come across that have two rounds. All the others have a deadline and go through everything after that date.

I've not heard of this either; all sixth forms that I know of have only one round of applications.

If there are only 50 places, then I would go for the early round as there may not be any places left by the second round.
Do the rules prevent you from applying for both rounds?

I suppose the standard advice applies: talk to the admissions people and ask them the question!