I think it is very difficult to really make use of those performance tables.
First, you need to really properly crunch the numbers.
Then you need contextual info to interpret what is likely happening.
Then you need to consider what that means for you. For this, you need to estimate the future, and personalise it for your particular family/child.
Our school's results are a less great than they have been in the last two years, but the progress scores have slid way down.
I note for example that compared to recent years, the average score for reading/maths tests has come down at our school. But the % meeting expectations has stayed high. % getting greater depth has gone down. Progress scores are worst for 'previous high attainers' but bad for 'previous middle attainers' too. So I guess this was a high achieving cohort at Y2, that hasn't made as much progress as other high achieving cohorts (in the country, and in previous years at same school). Especially the 'high attainers' weren't all able to convert their Level 3s (as they were in 2014) into 'greater depth'.
Contextual knowledge of our particular school then tells me that the 2018 cohort was a lot happier, over all, than the two previous ones. And also the rumor is that the two previous Y6 teachers left due to disliking all the pressure put on them (and onto Y6 kids) from SLT. 2018 Y6 teacher also left but after having resisted much of that pressure.
That again allows me to interpret the data differently.
But that is all looking back. What does it mean to me, my kids, looking forwards? OP's child is in Y1, nearly six years to go until KS2 SATS. My eldest has nearly three years to go. In our case, chances are that the school will continue going through Y6 teachers (in the last 5 years every Y6 teacher has left at the end of the year), so past experiences say nothing as to how our Y6 teacher will be. Will they put results over the kids' wellbeing? Will they resist the pressure?
The headteacher being in charge, chances are that teachers will be recruited that are results-orientated. This year's slide in attainment and especially progress will be seen as proof that the 'happy' teacher's approach doesn't work. So I'm expecting exam-factory and unhappy Y6 kids in the next couple of years.
The next question is, what does that mean for my particular children? And there again, the overall data says very very little. I am not too concerned for my eldest, as he is fairly resilient to pressure. My younger child is too young yet to predict how she would deal with a potentially highly pressurised Y6 in six years time. By when there may be a new headteacher, and new priorities, anyway.
All that said, I am actually rather pleased at the slide in results, as it just might make the governors sit up and take notice, as opposed to taking the headteacher's word for gospel.