The scores for the schools in my town were that only 20% of the kids in elementary school were reading at grade level, and the math scores were worse.
My eldest child was a special case, at 4 she was already reading books. She had a large vocabulary for her age and was able to sit and pay attention to the task at hand. Unfortunately, her birthday was in November and the school district refused to even speak to me about putting her in school the September before her 5th birthday. I knew kids who were six months older than her and had none of the skills she possessed; but, that was not to be considered. I ended up putting her into a Montessori kindergarten, and then went the Catholic school route.
The schools can really be that bad. Hubby and I spent our own money to get a decent education for both of our girls. This meant scrimping on our budget, definitely no vacations. But, it was worth it. When they hit college they were definitely ready for the work. My youngest went through college for her bachelor's degree in 3-1/2 years.
I think a lot of the problem is not having moms at home with the child from birth. I would walk around with my babies and talk to them constantly. I read them little books, even as an infant. Children learn language from hearing language. They get that from one-on-one interaction with mom (and dad), not from a minimum-wage person, who doesn't really care and changes frequently.
I remember seeing a young woman, who I knew had a degree in teaching, use hand signals to communicate with her children, like they were dogs or something. It is silly stuff like that which really hurts children and affect the outcome for what a teacher will have in her classroom.
My own students also have the Spanish/English difference to contend with. Many have non-English speaking parents. If they come in for a conference, we have to have a translator. School districts are increasingly pressuring teachers to be bi-lingual.