How much harder are Barrons' practice tests? (Math II)

I know in old threads it says that Barrons is significantly more difficult than the actual exam, but is it still really that much harder? I am seriously struggling with the math II Barrons practice tests. Math has always been an easy subject for me; I’m a year accelerated for it at school and get A’s & got a 35 on my math section for ACTs with hardly any prep, but on these practice tests I’m getting high 600s and a few low 700s. I do like the idea of preparing for a harder exam and therefore being more confident and prepared when the real deal comes along, but holy shit is this discouraging and I’m not sure if it’s the book or me. Do I just need to start studying more or should I switch to Princeton Review?

I’m going to try my Bio M book from Barron’s now…a bit scared lol

Thanks!