It's a foot-in-the-door requirement, to make homeschooling burdensome to parents, and to force the students to physically come to the public school premises.
1. A requirement that students attend annual standardized tests.
2. A requirement that students attend a two-week preparation session for annual standardized tests.
3. A requirement that homeschooled students attend a supplemental twice-yearly progress exam.
etc...
This simply is the battle between Conservatives and Liberals. Most home school families are very conservative, and most often religious, specifically Christian. Liberals want to defeat everything that these families stand for.
I choose to have my children in public school, but I am very conservative and I support families who home school.
Here in TN there is a fight starting about funding of pre-K programs (long story short--lottery money that is supposed to be for college scholarship is probably going to be used for pre-K programs). Once government starts funding pre-K programs, the government will want to make it mandatory for there to be kids in those programs. Too early for requiring children to go to school, in my opinion.
Homeschoolers are at a disadvantage in state tests. Most homeschoolers do not learn all Science from an environmentalist wacko point of view. Or learn History from a America is always wrong point of view. Or Social Studies from a Gay/Lesbian is the preferred lifestyle point of view.
Many school districts and states test these sorts of topics in their "standardized tests" that they wish for homeschoolers to take.
Just as they always do ...."if only we had more money"
Translation from the "state"...so both of you parents just work 14 hours a day pay lots of taxes to the "state" and let us take care of the kids. Like Hitler said to parents..."we have them 8 hrs 6 days a week - what are you?
My guess is they hope to bring up school district test scores.
My school district puts their own info on and then labels as "homeschool" somewhere on the paper, but the statistics probably show up on their school stats.
Homeschooled kids in MA are not allowed to take the MCAS, even if they wanted to!