Century Schoolbook for starters.

Sassoon for seconds.

hhp

More recently – Comic Sans.

The following references may help:

Walker, S. & Reynolds, L. (2002/2003). ‘Serifs, sans serifs and infant characters in children’s reading books’ Information Design Journal, 33(2/3) pp. 106-122.

Walker, S. (2005). ‘The books that nobody sees: typography in children’s reading books’ Baseline, No. 48, pp. 25-32.

Walker, S. (n.d.) Testing typography in primary schools [online]. Available at:
www.kidstype.org

Coghill, V. (1980). ‘Can children read familiar words set in unfamiliar type?’ Information Design Journal. 1(4), pp. 254-260.

Thank you very much guys !

Hello Stine,
Thank you very much for your most valuable feedback.
I am going to try to get the articles that you mentioned.