Dear Port Lavaca, Texas:
The age of consent in Texas is 17 (Texas Penal Code Section 21.11), so if both of them consented, it doesn't look like either one would be charged with a crime. However, that won't excuse liability for child support.
Lawyer
Trial Lawyer, 14 Years Experience
Both the 13 and the 16 year old are under the age of consent, so neither should be criminally liable -- unless there is force by one or the other. Once the sixteen year old turns 17, there's a problem -- just not now.
If Child Protective Services has investigated the matter and closed the case, I'm having trouble understanding why the principal is not accepting CPS's findings. That is what CPS is there for.
However, since the principal is threatening to call the police, I suggested that you contact a criminal attorney and let him or her know what the principal is threatening; and see if he or she has any recommendations for you.