Any tips on helping my son learn irregular past-tense verbs? Things I can do at home?

Make flashcards of the verbs (don't put the verb on both sides, use only one side). You can play memory, go fish, or just time him to see how long it takes to go through all the verbs (kids usually love trying to do things as fast as they can). You can also use the flashcards while playing board games. Before he gets to go, he has to pick a card, say the verb, say the past tense, and use it in a sentence. It's great for him to hear you play too, so you can model. I also play a version of tic tac toe with my kids. In each square, I write a verb, and before my student can put an X or O, he must say the past tense and say it in a sentence. Try Mad Libs! This will also help with other parts of speech. If your budget clears up, you can check out superduperinc.com, they have great language flashcards and games! Good luck!