Your thesis will depend on your opinion about the topic and whether you think the effects of homeschooling are positive or negative. Here are some typical answers:
Positive: children learn to be independent learners, families can teach children their own values (often religious ones), children can learn faster, and at their own pace, homeschooling eliminates problems with bullying, and traditional schooling means students waste a lot of time that isn't directly related to learning.
Negative: students don't learn to make friends, children don't learn socially acceptable behavior, parents don't always know how to teach effectively, children may not meet normal educational standards.
These are just suggestions. You should pick three or four effects that you think are important and put them in a sentence like this:
Three of the most important effects of homeschooling on children are:...