According to
The Signal Tribune:
"Kenneth... was enrolled in Fairgrove Academy on Oct. 18, 1977, but the last day he attended school was Oct. 27, 1977...
Kenneth’s body was found on June 3, 1978, on Division Street east of Corona Avenue in Long Beach."
The
distance from the middle school to where he was found is only 30 miles.
I know people didn't travel as much back then as they do now, but still... seems pretty close to have gone seven months without being noticed.
Then again, the article mentions that Kenneth "was a runaway from La Puente who had never been reported missing." (Wonder what that's about.) If no one was looking for him, it makes sense he could be nearby without being seen.