Can anyone remember them at school other than the time it snowed them in?
Todd (or was it Rod?) performed in the school orchestra with Lisa. And I think I remember Ned at a PTA meeting.
I remeber Ned at the PTA meeting.
They’ve also been in several school assemblies. Shocking, considering that Springfield does have a fundamentalist school.
I think it would fit with Ned’s frugal ways to send his kids to public school, since his taxes are already paying for it.
It would further fit with Ned’s worldview to greet the boys each day as they arrive home from school and show them how everything they learned that day was wrong. 
Flanders
“Ow! My eyeball!”
Todd got nailed in the eye by a paper airplane (thrown by Bart) at a school assembly. Rod was seated next to him.
Todd also appeared in the school uniform/Homer’s bowling team episode. He was playing a very dispirited game of tag with Lisa and Milhouse.
I was actually just wondering the same thing earlier today! On the one hand, Ned seems like the home-school type. Also, Rod and Todd never show up on the playground, shoolbus or school trips. Neither of them is in Bart’s or Lisa’s class (is one supposed to be a year ahead of Bart and the other a year ahead of Lisa?). But the examples everyone has come up with seem to suggest otherwise.
In the teachers strike episode Ned chairs the PTA meeting and calls it to or-diddely-order.
I think I remember seeing Rod (the younger one, right?) in Lisa’s class at least once.