If it is hard to verbally state why you have concerns, bring your child’s work samples with you to the school to show what is hard to articulate. A full psycho-educational assessment should give you the answers that you seek.
Before going elsewhere, you might want to find out exactly what services the school system could offer you – and when they could provide them. If the timeframe or suggestions for providing needed services is unacceptable to you, there are independent educational testers that you can go to privately. The following articles will give you an idea of what to expect from the testing process:
There are several national organizations that can help you through this process and provide referrals to local professionals. You can contact the International Dyslexia Association or the Learning Disabilities Association.
Be a good consumer in this process. Ask potential testers, tutors, and consultants about their experiences and specialization before you choose a provider. You want to make sure that the person you choose will be a good match for your child.