There is nothing in Wisconsin law that requires public schools to accept credit transfers from HBPEP’s. The institutionally-driven mission and purpose of public schools does not neatly align with the parentally-driven mission and purpose of homeschools, and each institution gets to set their own rules for the administration of school credits.
If a previously homeschooled student wishes to transfer credits from their HBPEP to their public school, they will need to advocate for themselves with their local school / school district. Public schools can use a variety of assessments to decide on placement. Transcripts are only one kind of assessment; other kinds include completed work, interviews, outside testing, and school placement tests. Each parent will need to advocate for their own children, but once a child enters the public school system, the school gets to set the rules for assigning credits.