From an elementary perspective, third grade is not the hardest. 2-3 is the sweet spot it think with 2nd being the most preferable. K and 1 there are a lot of behaviors, learning school rules and needing to mature. Also a lot of unidentified learning and behavior disorders, so no support. 4-5 they are too cool to want to impress their teacher anymore. Lots of behaviors because of that. 2-3 they are still little but more mature. They generally want to please their teacher still. 3rd grade is a transitional year because they are reading to learn instead of learning to read, which can make it a little challenging. Every grade and age has pros and cons. All elementary teaching positions are a lot. Especially compared to middle school teaching of one subject that you teach over several times. Middle school teachers also seem to have more prep and less meetings. At least in my experience.