What does this progress 8 score mean?

Not many schools will get to 2-4 for P8.

What is 2-4. The max for Progress 8 is 1

Means the school is probably in the top 1% in the country for progress that pupils make between KS2 and KS4. It has it's pros and cons.
Pros- can show that just because a school gets good GCSEs it doesn't mean they're better than the school down the road that gets worse results. Progress 8 shows how much progress kids have made from y6 sats to GCSEs, some schools just get very clever intakes so GCSE grades aren't necessarily a good indicator of progress, as those kids started off clever so should be passing anyway.
Cons- Lots of primary schools are under pressure to have good sats results so really drill their kids in the test, meaning they get artificially high scores that aren't an accurate representation of that child's ability. That child starts secondary school with very high targets that aren't sustainable and their secondary will look like they've failed them. Equally schools that get kids from very bad primaries may find it easier to get high progress.
Progress 8 obviously doesn't include kids who didn't do sats, so schools with a high intake of kids who haven't done sats, can't include them in their scores even if they've made tons of progress.
I may be wrong on this but schools can only include kids who were in the school in y10 and 11 meaning a child who entered late and the school put a shift in to catch them up won't be included.
It's calculated using buckets and subjects that aren't so academic get less points per bucket.

Generally speaking it's a good snapshot but I wouldn't put all your trust in it. Besides, this won't be around for the next 2 or so years as the COVID y6s didn't do sats so there's no comparison. I would filter their results by prior attainment. It's a good indicator of what results children with your child's ability get. Eg for my DD I've always checked how many low prior attainers pass, as that tells me their support for Sen is probably quite good if more than 20% of low prior attainers are passing.
The breakdown of how many kids are in each group ( low, middle and high prior attainers) is also a good indicator of what type of intake they have. Some schools are very bottom heavy, meaning lots of kids are in the low or middle bracket, it may be because they're in a grammar area, or they just have a reputation for supporting Sen well which tends to put off parents with high prior attainers.

Op any positive figure is good. Not many schools will get to 2-4 for P8.

So it looks good to me. What are your other options if you don't like all girls? I'm not a fan either but I know lots of ppl, whose opinions I value and respect, who have had positive experiences with single sex.

Essentially means that pupils on average are performing half a grade better in their GCSEs than they were expected to according to their KS2 scores in their SATS
A minus/negative score indicates the school isn't performing very well because the student is making less progress than expected

This explains it: