Once children feel well enough they are aloud to go to school. The disease especially in children does not tend to be serious. Herpes Simplex is the cause of Cold Sores. It is a direct contact infection. It is not serious.
Aseptic meningitis is mentioned.
The name meningitis is scary but aseptic meningitis is rare and self limiting and people get better. It is much less serious then bacterial meningitis. Likely of greater concern is that direct contact with the genitals can infect the genital area, which in turn can be very serious for a new born baby. Herpes Simplex is spread through contact with infected secretions, usually infected saliva. It is generally considered that direct contact is needed.