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schoolPreschooler development
Preschooler test
Preschooler test or procedure preparation
School age child development
School age test or procedure preparation
School-age children development-based time out plan, with the provision that, after the time out period, he should play by himself for a bit prior to joining other children. After a couple of weeks, if the behavior is not better, add a plan whereby you follow up at home. For safe behavior he can earn privileges (e.g., TV time, outdoor play, treat); if he is aggressive he does not earn the reward and you can implement a brief time out as well.
Any change in familiar routines can certainly de-stabilize a child, and the alteration in the contact with his father may be playing a role.