It is necessary to get a child's tonsils out if they are enlarged?

No. Tonsils & the other lymph glands then to grow a bit faster than kids until 7-8yr; then stabilize while the kids continue to grow larger. It is common for the tonsils to appear large in middle childhood & kids to snore in sleep, only to seem smaller by the teens when most snoring stops. Chronic tonsil infections, tonsil abscesses & sleep apnea are the primary reasons removal are considered.