Charter schools are public schools that offer other philosophies and curriculum from the regular schools. Some are good some are not. You need to do your homework and look them up just as for any school, on the web, visit any schools of interest, check on their financial stability, consider their philosophy, and see if it seems like a good option for your child. Some also go beyond the elementary grades. My daughters school goes from Prek all the way to 8th grade, they have a Montessori philosophy and incorporate other brain based curriculum as well. The staff work well together, and the school is intended to be more holistic then regular schools, and consider the whole child more than many schools. They originally had lunch delivered from the local high school, but now do their own healthy lunch program, and incorporated gardens and healthy curriculum into their classes.
Magnet schools are public schools directed at a specific area like arts, science, math, tech etc. They still use all the other subjects, there's just more concentration and availability in whatever magnet area they are dedicated to. So if your child has a strong interest in the area the magnet school is dedicated to, or if they are good at that area this can be a good option to enhance the skills and options for them in that area.
As with any school each is different, each has it's own strengths and weaknesses, and they should be evaluated according to the values you and your children find important. There are other regular public schools that also are very good, and others that aren't. You just have to look at each one individually, make sure your child is comfortable in that environment, see how the teachers and staff interact amongst themselves and with the children, and be sure that the philosophy meshes well with your ideals. It's also a good idea to find out how they intend to improve the school in the future. Are they going places, are they looking forward and trying to improve, or are they standing still and not trying to improve? Whatever the case may be, they need to have the children's interest and welfare at heart.