I don't think it's a teacher thing, but maybe generational? Both my mother and MIL were teachers and they are like this, but so is my father who was an exec. My FIL is the only one out of all of them who seems to get that grandparenting is supposed to be about fun - goofing off, being silly - not doing all the battles of parenting all over again (often in ways that contradict the preferences of the actual parents!). Now my sister is also a teacher but she is all about giving her kids their autonomy. I feel like current parenting thinking is about letting our kids figure things out on their own, make their own choices and experience natural consequences, etc. But my parents weren't like this when I was a kid and they are the same with my kids - just really pushy, and they can't handle the meandering ways of children so they feel the need to force things. It's crazy annoying. I think they think that I am just too overwhelmed (we just had our 3rd 6 months ago) to keep a tighter ship, when in fact I've chosen to reject their parenting style. But they live far away so as long as they don't cross the line beyond annoying/nagging, I let it go so as not to spoil our visits (the controlling ones are always the touchiest to criticism, too, no?). Plus I'm not going to kick a free childcare-horse in the mouth!
