I haven't read any of your answers, but let me say this. 1. You are 36 years old. It's harder to get pregnant when you are older. 2. I have had 2 children *so far* whilst attending college, and have four total. The additional children don't really make it harder to go to school, but then, I am blessed with being able to go and not put my kids in daycare.
Ok... I was the youngest in my house. My brothers were 4 and 5 years older than I was. I constantly was made to feel like I was in the way (could have been my sex, but I think age had a lot to do with it as well) and I ALWAYS felt alone. I was a very lonely girl surrounded by three older brothers who wanted nothing to do with me.
Family planning isn't anyone else's business (I want a fifth and am constantly being asked when I will stop, as though 5 children is a huge difference from 4 lol) but everyone has an opinion and feels the need to share theirs. Personally, I think a 4 year spread is too large, also, you have to remember that it can take up to a year or more for you to get pregnant. If you start trying when your child is 3.5, you may not get pregnant until they are 4.5 and then you have another 9 months being pregnant, so the real spread would be 5.4 years... and thats only if you do get pregnant right away. Just something to think about. Plus, it's not too difficult being pregnant while attending school, as long as you are lucky and have a problem free pregnancy. I had my last in July, so I have a good 2 month window before school starts up again. :)
Of course, saying all that, I fail to mention that my oldest is 13 and the next one down is 5 (then 3 and new baby)... the 13 year old was 7 when the second was born and was really excited and helpful, but now she's not so excited. For one, when I get pregnant, it's proof that her parents have sex and that's just gross. :P Anyway, good luck on TTC when you DO, and don't let anyone discourage you. have fun too!