As a homeschooling parent you are aware that there will be some subjects that you may not be very comfortable handling after a certain grade level. The basics are easy for you to teach in any subject, but if you have limited experience with teaching science, you and your child could get frustrated as the level goes higher and you are unable to answer all his questions. There are a few simple ways to deal with this challenge of teaching homeschool science.
Use the expertise in your local homeschool support group
It is more than likely that you already belong to a home school support group in your city. You can tap members of this group who are better qualified to teach home school science than you are. They can take the science classes for your child and you can either pay them for this or trade off classes for their children in some other subject that you are comfortable handling. It would be a mutually beneficial relationship.
Consider online homeschool classes with a science course related to their grade
If you are not a member of a homeschool support group, or do not have a person who is comfortable handling science in the support group, you can consider an online science course. The student can learn science on the computer with the help of online teachers. Just because they are learning from an online course does not mean that they are not being homeschooled. Plus they will have the benefit of more than one science teacher as most such websites hire a number of professionals to help with the courses.
Send them to a private school for just the science subjects
If you feel that computer aided instruction is not an option you could consider sending the children to a private school in the vicinity just for the science subjects. They do not have to attend regular classes, just subject specific ones. Another alternative would be to approach the science teacher in such a school and ask them to consider private tuition for your children. You know what will suit your needs best. So consider all the options well before taking the final decision.