Chris PrattandAnna Farisgot back together Wednesday ... not in a romantic way, but to celebrate their son,Jack! The two megastars attended Jack's promotion from sixth grade at a park in Santa Monica ... and, it seemed like a fun recreation activity for the former husband and wife paying. Check out the pics ... CP and AF are smiling while posing on the sides of Jack -- keeping the reason to stay amicable in between them. They even embraced at one point ... proving they're doing their best to keep any animosity regarding their split behind closed doors. As you know ... Anna and Chrisannounced their separationin 2017 after nearly a decade together, finalizing the divorce the following year. The two have since moved on ... with Anna marrying cinematographerMichael Barrettin 2021 -- while PrattmarriedauthorKatherine Schwarzeneggerin 2019. Pratt and Schwarzenegger were pictured chatting with Faris and leaving the event together. BTW ... Jack was born nine weeks premature and weighed just three pounds when he was born in 2012 -- and, both Faris and Pratt have talked publicly about his uncertain health early on in his life. But, he looks happy and healthy here -- with a couple of parents who clearly adore him!