Repeat 7th grade to get into Lowell?

I am a parent and have a son at Giannini.  He started Kindergarten even though he didn't turn 5 until early October, and now I see he would be one grade behind according to the new law.  I wanted him to get into Lowell, and he is getting a couple Bs now.  I'm trying to get him to work harder to fix this, but I was thinking maybe he should repeat 7th grade.  We mostly spoke Chinese when he was little and he is struggling in English and Science.  I feel he started too soon and it would be far better for him to start life one year later as a Lowell graduate than a year earlier at Washington or, due to SFUSD Policy, maybe at Mission or Galileo, there's no sure thing, we live close to Washington but that doesn't matter.  Do you know if I could have him repeat 7th grade so he can improve his skills and get into Lowell to have a better future?  What is the district policy on this and how do I request it?