Scanned below is the first schematic I ever drew, of a device I built from various parts I had (in large part, electrical components where what I had as "toys"). When I drew it I had just learned to read and write, as can be seen from my multiple misspellings which are mostly sounded out words (although I managed to spell "knob" correctly), and not so great handwriting (actually my writing hasn't improved dramatically, but at least my lower case a's are better). At the time I would have been in first or second grade, and 7 or 8 years old.
In large part, I can still remember mostly what this looked like, and this is probably because I took the time to draw it, and the drawing keeps my memory of it active. To anyone else it may not look like much, but I know what I meant. I have an "updated" version below, where in red I have the text which I meant to write (spelling corrected), and in blue I have additional comments.
In the upper left corner, what is drawn is a small wooden "table", which was basically part of a wooden toy construction set. On top of the table I had several batteries (probably D and/or C cells) connected in series with wires taped on. At the time I remember I would always try to put as many batteries in series as possible to get as much voltage as I could. There was also a tap somewhere in the series, which I label as "low", and I connected this to the ground terminal of an electrical outlet (at the time I didn't understand the concept of what the ground terminal on an outlet was for). I used to collect the ferrules of pencil erasers at the time, and here I used the ferrule to act as a crimp splice for the "low" wire.
In the box labeled "phone place" I had a telephone (maybe two) which was powered by the batteries. I don't remember exactly how I had everything connected, but I remember at the time I was drawing this thinking that anyone looking at this schematic will wonder how things are connected in there. I think I just didn't feel like having to go into the detail to draw that part up. Coming from the "phone place" I have a curly wire going to a switch which then turns on/off power to an electrical outlet and an incandescent bulb socket.