Milan has many international schools for kids aged 1-19.

Follador Nursery School, age 1-3
The Kinder Garden, nursery school age 1-3
International School Milan, all levels age 2-19
St. Louis International school, age 2-14
Ecole Française de Milan, Lycée Stendhal, preschool and elementary school
British American Pre-school, preschool age 3-6
Sir James Henderson British School, all levels age 3-18
Deutsche Schule Mailand, German preschool, elementary school, middle school and high school
Swiss School of Milan, all levels
Bilingual European School, elementary and middle school
ミラノ日本人学校ホームページ, Japanese elementary and middle school
American School of Milan
Bilingual Elementary School of Monza, age 5-11
International School Monza, all levels age 2-19
International School of Como, pre-school and elementary school, age 3-11
European School Varese