A kid named Jack who comes from a devout mormon family who all wear the infamous Magic Underwear starts going to kindergarten and starts getting bullied and after that he starts questioning his faith.

Nice one liner Richiev!

No need for character names in a logline unless absolutely critical to the plot (i.e the character is Jesus for example).

In addition to Richiev's comments the logline has some poorly worded actions and events as a result the logline is too wordy.
The MC starts doing something three times: "...starts going to kindergarten?", "...starts getting bullied?", "...starts questioning his faith?".

In story a character doesn't start to do anything he or she just do it. The MC goes to kindergarten then he is bullied and then he questions his faith. However, which of these actions is critical to the plot? Use the critical action and drop the others.

Hope this helps.

Not often you see a story about the positive effects of bullying :)

It seems the inciting incident is the bullying, but the response; a 5 year-old questioning his faith seems a bit far fetched.

That doesn't mean a five-year-old's spiritual quest can't work, however it might help if the five-year-old had more of an outer goal instead of an inner goal.

The five year old get's bullied so him must 'do this thing' in response.

Hope that helped, good luck with this!