3 Answers

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There are many different children needs. If you refer to basic needs, and if you are not sure you know what your kid need in general, you can consult with your parents, friends, or seek profesional help, such as social workers.
If you are referring to cognitive/learning needs: some kids are gifted and are able to study more than others, and sometimes even achieve an academic degree while in high school. On the other hand, some kids have learning disorders, hyper-activity, or other difficulties. Clues for these conditions and others can be observed by parents or teachers. If you suspect something in particular you can search it on the internet or consult with your kid's teacher.

Yes there are "benchmarks " which are physical and mental tasks that a child of a certain age usually does.  Your pediatrician will be watching for these, however, if something seems delayed, bring it to their attention.  Also, most states have "early intervention" services, and you may request an evaluation.  If a child has a need they will have therapists work one-on-one with your child.  If at the age of 3 the child still needs assistance, then the school dept. begins following the child in their special education system.  Many services are available, my grandson for example gets sponsorship through the Shriners, who fund some activities to assist with his fine motor skill development.  Good luck.