I have almost 5 stars education rating. I think it is 4,8

Franchise mode, game year 75, 2,6K guests, 9 habitats, 80-85 animals.
I have 2 info booths selling audio guides at the default price.
I have 3 or 4 conservation boards.
Every habitat has 1 or 2 habitat education boards fully powered. Make sure, you have enough fully trained mechanics to keep them in order.
Make sure, all your animals are fully researched.
The biggest impact for me is educational speakers. Make sure they are powered. Turn the volume up as much as you can, but the sound radius can not interfere with each other. If you see the red areas in guests' education heatmap, turn the volume down. Make sure that your guests swimming and diving in the blue sound radius as much as they can. The closer to the path your speaker is, the better. It is OK even to put your speakers near the closest shops or picknick tables. When guests stand in a queue or eat, they get educated.
The same habitat speakers can only educate a guest a little bit. If you put 10 speakers on the same animal species, it won’t do much good. The education bar goes up slowly then stops, when your guest gets all the knowledge about that particular species. Your goal is to force your guests to visit all your habitats and exhibits to gather all the possible knowledge. So the easy zoo navigation is another goal in education.