How can I reliably check my 13-year-old's temperature at home before sending him to school?

I can’t read his temperature for you, but I can help you get a reliable estimate and decide next steps.

Short answer

• If he feels hot to the touch, is shivering or flushed, or has recent vomiting/diarrhea/lethargy, treat him as febrile and keep him home.
• Use an oral thermometer correctly (best available option). If you only have a single-use or underarm (axillary) thermometer, know its limitations and how to improve accuracy (see steps below). If you’re uncertain and he looks or acts significantly ill, contact your pediatrician or urgent care.

How to get the most reliable at-home temperature without ear/forehead devices

1. Use an oral digital thermometer if you have one (most accurate common home device for older children). Steps:

   • Wait 15–30 minutes after he’s had hot/cold drinks, been mouth-breathing heavily, exercised or vomited.
   • Have him breathe through his nose (if possible) or close his mouth around the thermometer gently.
   • Place the tip under the center of the tongue toward the back; ask him to close lips around it and keep it there until it beeps (usually 30–60 seconds).
   • Read the number. A reading ≥100.4°F (≥38.0°C) is considered fever.

2. If you only have an axillary (underarm) thermometer:

   • Clean and dry the armpit. Place the thermometer tip in the center of the armpit.
   • Hold his arm snugly against his side for the full measurement time.
   • Add about 0.5°F to 1.0°F (≈0.3–0.6°C) to the axillary reading to estimate an oral temperature. Axillary tends to read lower and is less reliable.

3. If you have a rectal thermometer (often used for infants but accurate):

   • Rectal measurement is very accurate, but in a 13-year-old it’s usually unnecessary and can be uncomfortable. Only consider if you cannot get an accurate oral reading and you know how to use it safely.

4. If your oral thermometer keeps reading normal because of mouth-breathing:

   • Wait until he can breathe through his nose (use saline nasal spray or a humidifier to relieve congestion first). Give 15–30 minutes after clearing nasal passages before rechecking.
   • Alternatively, sit with him and ask him to close his mouth for the measurement and breathe through his nose if possible.

Other clues that indicate fever even if thermometer reading is uncertain

• Feeling hot to touch on forehead/neck/chest, especially compared with your own skin.
• Chills, shivering, sweating, flushed face, decreased activity, poor appetite, irritability, headache, body aches.
• If he is vomiting, dehydrated, very sleepy, confused, has breathing difficulty, severe sore throat with drooling/difficulty swallowing, or a rash — seek medical attention.

Treatment and when to keep him home

• If he likely has a fever (symptoms above or estimated temp ≥100.4°F), keep him home until fever-free for 24 hours without fever-reducing medicine.
• For comfort: ensure fluids, rest, light clothing, and antipyretic medication if appropriate (acetaminophen or ibuprofen; follow dosing instructions for his weight/age or ask your pediatrician or pharmacist). Do not give aspirin to children.
• Contact his school if they require a specific documented temperature; explain the measurements you’ve taken and follow their policy (some schools require an in-person medical clearance).

When to call a doctor or seek urgent care

• Difficulty breathing, persistent vomiting, dehydration (very few wet diapers/urine, dry mouth, very decreased urination), severe sore throat with difficulty swallowing or drooling, neck stiffness, severe headache, rash, high fever that does not respond to antipyretics, or altered mental status.
• If you cannot reliably measure his temperature and his symptoms are concerning, call your pediatrician for guidance or get an in-person assessment.

If you want, tell me what kind of thermometer you have (digital oral, axillary, temporal, infrared, old mercury, disposable strip) and his current behavior/symptoms; I can give step-by-step instructions for that device and help interpret the result.