I think it is safe, and good for him, to be able to walk to school. Don't be surprised, though, if other parents, teachers, or just nosy people question your decision.
A neighbor of mine had the police called on her because her 2 kids, 10 and 8, were playing soccer in the public park without supervision. They weren't causing any problems at the park, it was a Saturday afternoon, the mom knew where they were, but they were ESCORTED HOME BY THE POLICE. The police said that they had to do a "wellness check" because they had received a call from some busybody.
The more freedom kids have, the more they learn, and the more they become competent at life. I think the cellphone with GPS is the best solution for our family. And I think even younger than 10 years old is plenty old enough. An older phone would be fine, and blocking internet is easy; you can even set it up to only call certain people, and shut off at night. And if he's going to a neighbor's to play, he can call you when he arrives there, thus learning responsibility that will come in handy when he's a teenager.
I read a column years ago that really resonated with me, let me find it.
Ok, this is an update
https://www.washingtonpost.com/post...way-alone-i-got-labeled-the-worlds-worst-mom/