Which is why I learned how for forge both parents signatures by the time I was out of 2nd grade. One missed field trip because my parents couldn't be bothered to sign the form was enough.
Started out tracing them on a thin sheet of paper. Took about a months until I could do it easily freehand. I had the best mimic out of all of my siblings and would often sign their's as well.
Hey funny story related to this. My father died when i was six. (Not the funny part). In high school i started signing early dismissal letters with my own name and the school never questioned it.
In our house, the policy was I (mom) used my real signature, kids forged their dad's signature when needed. So, my signature was mine but his signature was always forged.
This says high school, but honestly probably not as long as they don't try too hard. My signiture is some squiggles with a line and dot thrown in. A first grader might actually try though, then it could be suspicious.