Many district have their own versions of "Algebra readiness test". But our district says it's Iowa and I gues this is what they means...

http://itp.education.uiowa.edu/iara/iara.aspx

Basically, pre-algebra is in regular 7th and 8th grades curriculum and they are testing the same thing as in 7th and 8th grades level. Algebra is HS Math credit class and if the student is in 8th grade going to 9th and if the he/she gets 70, he/she is ready to go. But for student acceleration, they have higher benchmark. Our district benchmark used to be 90 percent but the State law makes it 80 across the board. You need to check that with your district.

There will be gaps. There are online resources from textbook publishers and if your DS can take those Chapter tests and you can find out what the gaps are and fill in during summer time.

http://glencoe.mcgraw-hill.com/sites/0078740479/student_view0/chapter1/chapter_readiness_quiz.html