Another Patsy place I was able to find - once I knew it was Crockett California where she grew up. The picture at the bottom that was labeled "Patsy by Carfuinez Grammar School Tunnel Jan. 8, 1939". The reason I couldn't find ANY thing about it previously (in addition to not knowing about Crockett) was due to mis-reading Patsy's Mom's handwriting. It wasn't "Carfuinez", it was ""Carquinez"! Once I figured that out, I also found this other anecdote online from a previous student. So now we know what the tunnel was actually used for.
https://www.pressdemocrat.com/news/2314613-181/life-changers
"I was a freshman in high school. That year was 1963. I was excited to graduate eighth grade and enter John Swett High School in Crockett, California. The tunnel under the main street in Crockett connected the grammar school, Carquinez School, with the high school. Grammar school students were not permitted to go through the tunnel that connected the two! I remember delivering a hand written note or two from my eighth-grade teacher to a teacher in high school. They were dating and this was before cell phones. I felt so honored to be able to walk the distance with such permission!"
Couldn't get a modern view of the tunnel via street view, so I had to go to the overhead satellite view. That white thing on the side of the road is the tunnel. You'll notice it no loner has a curved roof like it did in Patsy's day. Those red brick buildings are the John Swett high school across the road.
In this one we're looking back at the Carquinez Grammar School from the high school (tunnel in lower left quadrant). Even though the building is still there, I don't think the grammar school is still a school. There are no signs or anything indicating that it's a school. Looks like it's been turned into some kind of apartment building (like a lot of old schools like this tend to be))