Would you hold your child back a year in school for kindergarten?

Little back story, my son is finishing up his kindergarten year and just turned 6 last week, his teacher had suggested and referred that he do kindergarten over again because he is behind. He has trouble recognizing which letter is what in the alphabet. He knows 15+ letters and just about 10 he really has no idea. He knows the alphabet song of course. He can recognize about 50% of the sight words and is great at math can write to 100 add subtract all that. I understand he is not as far in the letters and word department but I feel as if holding him back in kindergarten wouldn't help him. The school he goes to is only 3 hours a day with 28 students. I feel like moving forward with his education to 1st grade would help him. I also know a 1st grade teacher who has offered to tutor him this summer. I have his retention meeting next week with his teacher and school counselor and I plan on telling them I will not hold him back but will continue to work with him, my question is what would you do? Any teachers on here how do you feel? I remember when I was in kindergarten al we did was art and story time now they test and do homework I just don't get it!