My suggestion would be to build a great base of a GPA in 9th and 10th grade. I personally do not believe that HA schools care as much about rigor in 9th as they do in 10th, then 11th and 12th. Build it. 1-2 AP's/honors as Fresh, then 2-3 as a sophomore, 3 as a Junior, and then see where you are at as a Sr.
A 3.5 GPA (unweighted as HA could care less about weighted GPA) as a Freshman can be really difficult to get to a 3.75 by end of Junior year. Especially as AP's and honors classes get more difficult and if baseball matters (you are here right?!?) your kid is going to be eating/studying/practicing/lifting/repeating a lot his sophomore/junior year. Add in girls and who knows what things might look like.
My 2022 had 2 A's and 4 B+'s in 9th (3.55), then 4 A's, 1 B+, 1 B- in 10th (3.69 & 3.63 cumulative), 3.69 & 3.65 after 11th. The school profile matters to HA schools, the extra curriculars matter, rigor matters, and ACT/SAT matters (or can help a lot if you have a good score). And you have to be better than average at baseball if you want to play at an HA that is good at baseball.
My kid had one B- in his first 3 years of HS. Zero B's and 8 B+'s. The B- teacher was his worst teacher (and many kids worst teacher and grade in 3 years...it was an honors class btw). I would not settle for a B as it could really hurt if there is a challenging class, teacher, or extenuating circumstances later in HS. If your kid cant move back up to honors sciences then I might "settle" for a B but if he can then I would drop down, book an A and rigor up for rest of HS.