I'm another one echoing what's been written above.
You fill in your child's information when you get admitted to a school. It goes on the school's database (usually Simms or integris or something). The information is there, but staff only tend to access it for something specific.
So, the information that's logged is contact details (name, address, phone number/email), gp/any health information/allergies. Any SEN. Siblings. Attendance. Languages spoken, religion. Whether the child is pupil-premium (free school meals in old money) Possibly attainment (this isn't relevant to my job, so I've never looked up a child on there, so don't know whether this is logged or not, but have seen a thing you can click to go and look, but I don't know whether teachers use this or not)
What parents do for a living is not included in this in any system I know.
I PROMISE that NO teacher thinks "ooo, I wonder about Rebecca in Yr 2 and goes to look them up).
Teachers tend to use the information only when they need to look up something specific. EG (most commonly), "we have a trip tomorrow, parent hasn't given consent, so I need to phone them to get consent so their kid can come along"
If your "personal thing" is something like "abusive ex" then it wouldn't be on the system, but would be filed separately in safeguarding and be on a 'need to know' (eg - Dad issued with Non Mol and court-ordered not allowed to collect. That information would be given to class teacher, anyone who releases [eg - PE teacher or TA] and reception staff)
Generally, school staff don't give a toss what parents do for a living. Unless it impacts on the child (eg - parent a surgeon, might be late to pick up due to not being able to leave an operation)
Schools care a LOT about being able to contact a parent or named person, so PLEASE, if you're someone who changes your phone number as often as I change my pants, make the school office aware of your contact details. Because if your child is ill or injured, we need to contact you to let you know and to take your child to hospital. It isn't very nice for your kid if we have to 999 it.