@Hnslovesyou1 - it's not that you are "tax-exempt" because you have a child. It's that based on your income and the tax credit you are eligible for the child(s) and any EITC credit you are eligible for, you are a due a refund comes April 15. The IRS tables that the employers are to use take that into account. Since the math the employer is using indicates a refund in any event, the IRS instructs them NOT to withhold federal tax.
if you want to "get into the weeds" of how your employer is supposed to be withholding federal taxes, look at the worksheet on page 9 of the link below . (it may be easier to follow on pages 11-12 as it will get to approx. the same result)
https://www.irs.gov/pub/irs-pdf/p15t.pdf
