1Where a child is not attending, the adults are often already cross with each other. That argument has to be parked before any plan will hold.
Home thinks the school did not act. The school thinks home is not firm. Both usually have a point, and neither point can be settled quickly enough to help this child this term. Meanwhile a plan applied one way at home and another way at school teaches a young person exactly where the gap is, and they will use it, not from malice but because it is there.
Islamic evidence
So keep to the right course as you have been commanded, together with those who have turned to God with you (Quran 11:112). The word together is carrying real weight in that sentence.
“So keep to the right course as you have been commanded, together with those who have turned to God with you. Do not overstep the limits, for He sees everything you do”
Qur'an 11:112
Psychological evidence
In a worksite trial with 107 distressed employees, acceptance and commitment therapy and stress inoculation training both reduced distress, although they start from quite different premises. It is one trial in one setting and says nothing about who was right about anything. It does suggest that arguing over whose method is correct can matter less than settling on something and doing it consistently.
Flaxman PE, Bond FW. (2010). Behaviour research and therapy · doi
Review detail
Why it works. A plan that two sides apply differently is not one plan, and the child notices the difference before the adults do.