School Blues

Kindergarten is stressing me out!
It all started when we kept Landen home from school last Thursday with a slight fever and headache.
He returned home on Friday with a folder full of makeup work and another with homework for the weekend. He was concerned about it right away, but I encouraged him that we would get it done and sent him to the kitchen for a cookie. Silently, however, I wondered how he would get the five worksheets, coloring page, and fire safety packet completed over the weekend.
This is Landen's schedule. He gets on the bus by 7am every morning and returns at 4:30pm (at the earliest) every night. He and his brother go to bed between 7:30 and 8pm after we read 1-3 of his library books. He never complains about the long days. It is because of that I want to keep his home time as sacred as possible--time to play with his toys, his siblings, or help his dad outside.
So, I was pleasantly surprised when he completed his makeup work and homework, little by little over the long weekend, without complaint. I felt relief as I sent him off to school this morning with his backpack full of completed work.
I did not have long to pat myself on the back, however. Tonight as I was wrestling a very unhappy Teresa into her pajamas, Landen took a break from tonight's coloring page to shout down the hall and tell me that I needed to sign and return all of his booklets because he only has four stickers on his pumpkin. Supposedly his friends all have "10 or 16" on theirs. (I'm actually impressed that he has four since I don't remember signing that many.)
He told me I needed to sign a reading booklet after he read it to me several weeks ago. I didn't see any directions to do that, but I signed it anyway to appease him. I hadn't heard another word about the booklets since. As they came home, I looked at them as I do all of his work, and threw them away at an opportune moment. (It is important to me to see what he is doing in school, but I cannot keep everything.) Now I find out that my son is delinquent in his sticker gathering due to my ignorance. Did everyone else know about this? Somewhere along the line I missed the memo. I thought I was a pretty attentive parent, but maybe not so much.
Why does this bother me so much when the student himself remains completely fine with his reponsibilities?
Could it be my oldest-child, overachieving, people-pleasing tendencies that got me through seventeen years of my own education? I might have to look into that.