They don't test for those - you have to do it privately. Or, if the school has evaluated and you feel like the evaluation did not catch or cover everything, you can request an Independent Educational Evaluation. FCPS will pay (to a certain amount) to have a private evaluation done. You can go to your own tester (you pay and get reimbursed) or choose one that is on the FCPS list (FCPS pays directly).
We just went through this and requested an IEE. The evaluation came back with dyslexia and dysgraphia, so we got that evaluation to FCPS for repayment and to the school and we will have an IEP meeting to regroup in the upcoming weeks.
My recommendation is not to rely on FCPS or the teachers. Most teachers are just not equipped to identify dyslexia, even if they were allowed to do so. Our school won't even let teachers tell you they suspect a problem.
Find a tester you like and have your child tested. It will cost $4000+, but it will be worth it because you will get ALL the info you need including recommendations for your IEP. We used
https://www.pascualvaca.com/ and they were fabulous.